tonight at ten: britain expels 23 russian diplomats after moscow fails to explain the chemical attack in salisbury. as the investigation widened today the prime minister announced a series of sanctions against russia and cut off all high level contacts with moscow. they have treated the use of a military grade nerve agent in europe with sarcasm, contempt and defiance. russia has again denied being involved and has demanded to be shown proof of a russian link to the nerve agent. the russian diplomats being expelled have a week to leave. we'll be asking who they are and what impact their departure will have. also tonight: i'm very proud that i have been able to contribute to our understanding of the universe. an extraordinary scientist who inspired millions — tributes pour in from around the world to professor stephen hawking who's died at the age of 76. students across america walk out of class — a month after the florida school shooting — in the largest protest against gun violence for years.

and what's in our bottled water? a special investigation discovers hundreds — even thousands — of tiny particles of plastic in a number of leading brands. and coming up on sportsday on bbc news... altior wins the big race on day two of the cheltenham festival. the favourite stormed home in impressive style to win by 12 lengths. good evening. britain is expelling 23 russian diplomats after moscow refused to explain how a military grade nerve agent was used on a former spy in salisbury. it's the biggest such expulsion for more than 30 years. the prime minister told parliament that the "undeclared intelligence officers" have just one

week to leave. the uk has also cut off all high level contacts with russia and announced that government ministers and the royal family will not attend the world cup. here's our political editor, laura kuenssberg. it was right to offer russia the opportunity to provide an explanation. but their response has demonstrated complete disdain for the gravity of these events. the midnight deadline came and went, leaving a morning with no new answers. theresa may went prepared to prime minister's questions, ready to announce the biggest diplomatic action against russia since the cold war. they have treated the use of a military grade nerve agent in europe with sarcasm, contempt and defiance. so, mr speaker, there is no alternative conclusion, other than the russian state was culpable for the attempted murder of mr skripal and his daughter. this represents and unlawful use of force by the russian state

against the united kingdom. so the uk will retaliate. the united kingdom will now expel 23 russian diplomats who have been identified as undeclared intelligence officers. they have just one week to leave. this was notjust an act of attempted murder in salisbury, norjust an act against uk. it is an affront to the prohibition on the use of chemical weapons, and it is an affront to the rules—based system, on which we and our international partners depend. so 23 diplomats suspected of being spies have seven days to leave, all high—level contact between the uk and russia is also being suspended, and no minister or member of the royal family will go to the world cup. and some russian state assets could be frozen, with possible new laws to crack down on hostile states. in a tense house of commons, jeremy corbyn was not quite ready to accept the culpability

of the russian state. our response must be both decisive and proportionate, and based on clear evidence. but listen to rising anger, asjeremy corbyn turns some of his fire on the tories. it is, as we on these benches have expressed before, a matter of huge regret that our country's diplomatic capacity as been stripped back with cuts of 25% in the last five years. it is tradition for the two main parties to stick together on foreign policy. not these two. this is not a question of our diplomacy, of what diplomatic support we have around the world. this is a question of the culpability of the russian state, for an act on our soil. fever rose. their continued disregard

for the rule of law and for human rights must be met with unequivocal condemnation. look, tories cheering labour backbenchers. jeremy corbyn‘s team, arms folded. the russian government has behaved with arrogance, with inhumanity and with contempt. anger displayed in westminster, that this is happening on british streets. in dorset today, the lorry that removed the skripals' car, seized. in salisbury, the bench where father and daughter were found, still sealed off. while the prime minister makes her opening moves in a diplomatic tangle that could last. tonight we do know it the prime minister felt tonight we do know it the prime ministerfelt she had tonight we do know it the prime minister felt she had little choice but to take firm steps in retaliation. we know the government

expects there to be some form of retaliation from moscow. what we don't know and what ministers don't know, what shape and form that may take. but we also don't know, there could be a prolonged period of tension between the two countries. but what is clear tonight, this is a big test ofjudgment but what is clear tonight, this is a big test of judgment for theresa may, and there may be nothing straightforward in the coming weeks and months, for making sure for her that she passes it. thank you. tonight, russia has again denied being involved and has demanded to see proof of the nerve agent used in salisbury. our moscow correspondent, steve rosenberg, joins us now. steve. there was little surprise. russia expected sanctions. what that was a lot of was a feeling of anger and defiance. there is a feeling that if britain wants a diplomatic war with

russia, then bring it on. in russia, at least the weather is showing signs of a thaw. after the long winter, moscow is melting. but in uk russian relations, you can feel the chill. britain's expulsion of russian diplomats has sparked anger with theresa may. prime minister may is destroying international law, and is destroying international relationship. of course, it is the end of her career. it's the end. it's a show. that was a political show. and this is not, it's not serious, it's not for the serious politician. and this was the show on russian tv, while mrs may was announcing sanctions. commenting live, andrei lugavoy, the man britain believes poisoned former russian agent alexander litvinenko in 2006. moscow refuses to extradite him. as for kremlin funded english—language channel rt, theresa may has left it up to uk regulator 0fcom to decide

whether it can keep its uk licence. what do you think the chances are of rt being censored in the uk? i hope rt is not censored in the uk, because i really would not like british media, including you, you are a very nice man, a gentleman, to be expelled from russia, which is exactly what i believe will happen if rt is censored in the uk. the british government wanted to send a strong message today to moscow. but that message has been dismissed here as nothing more than a provocation, and it plays into the narrative which the kremlin has been creating for some time, that the west is against russia. the man who styles himself as the defender of russia, came to crimea today, territory vladimir putin annexed from ukraine. with an election in russia in four days' time, uk sanctions may help the uk leader rally support.

with an election in russia in four days' time, uk sanctions may help the kremlin leader rally support. tonight, moscow is showing no signs of buckling under british pressure. russia is promising retaliation soon. steve rosenberg, bbc news, moscow. in new york the united nations security council has been told tonight that the chemical weapon used in salisbury was so horrific that it's banned in war. the us ambassador to the united nations said america believes russia is responsible for the attack and the un security council should take action. sergei and yulia skripal remain in critical condition in salisbury, ten days after they were the principal victims of an attack using a banned chemical weapon. widespread international outrage has now been echoed at the security council of the united nations, where russia is so often at odds with the key powers. britain's principal ally the united states, urged collective action against russia. time and time again,

member states say they oppose the use of chemical weapons under any circumstance. now one member stands accused of using chemical weapons on the sovereign soil of another member. the credibility of this council will not survive, if we fail to hold russia accountable. that's exactly the support britain was hoping for when it requested this meeting. but what of other punitive measures against russia? in the city of london it's less obvious if russians with corrupt or criminal money in britain, have much new to fear. unexplained russian wealth may now be pursued more vigorously, including some of the most expensive property in the world. the leading anti—corruption organisation, transparency international, estimates that a fifth of all property bought with criminal money in britain is owned by russians. but it's the expulsion of 23 so—called diplomats which is the big story.

at the embassy packing may ready have started. the government is convinced all those being kicked out are spies, and that the hit will hurt. whatever the effect turns out to be of today's action, the prime minister was bold in her claims. she said if the russians seek to rebuild their intelligence capability, we will prevent them from doing so. james robbins, bbc news, at the russian embassy. 0ur security correspondent, gordon correra, is outside mi5 headquarters. tell us more about these so—called "undecla red intelligence officers" who've been told to leave, and what impact their departure will have? it was striking the focus on intelligence in the prime minister's statement today. you could tell they picked 23 intelligence officers, because that was every single

russian intelligence officer who had been identified here at mi5, as operating undercover at the russian embassy. there are a couple of others who are not undercover. they are declared open intelligence officers. they have been left in place as a communications channel. the aspiration is ambitious. simply to dismantle russia's espionage capability here in the uk. other measures the government wants, including the ability to stop suspected spies at the border or port, something they can only do with terrorism suspects, and the ability to check private flights for freight. we do now how do salisbury attack was carried out, but you can see why the authorities want more power to stop people coming in and out of the country, and to check what they might be bringing in and out of the country. everyone knows the russians will respond. they may carry out tit—for—tat expulsions. i think the view in london is it will

not damage british intelligence in the same way, because we may not have as many spies in moscow, as the russians do here in london, but british officials also have some other measures in their back pocket ready to go in case the russians continue and try and even escalate the situation. thank you. tributes have poured in from all over the world for professor stephen hawking, one of the greatest scientists of modern times, who died this morning at the age of 76. he was diagnosed with a rare form of motor neurone disease when he was 22 and told he only had a few years to live. but he defied all expectations and went on to become one of the most famous physicists in the world, thanks to his studies on black holes and relativity. 0ur science editor, david shukman, looks back at his life. there is nothing like the eureka moment of discovering something that no one knew before. stephen hawking had a gift for inspiration, a powerful spirit overcoming an ailing body to allow a mind to roam through the cosmos.

it earned him a place as the most famous scientist in the world. it has been a glorious time to be alive and doing research in theoretical physics. who else could draw the crowds? this was israel. the man who gazed at the stars became one himself. his story both poignant and uplifting. his career involved concepts so alien and complicated that for most people it's been a struggle to keep up but he explored the strangest of features of the universe, black holes, drawing together the science of the very largest things in space with the science of the very small — part of a quest to come up with a single theory for the universe. he made these incredibly original insights which set up the modern theory of black holes, and made great contributions to cosmology, and so he was a huge figure. i was devastated, really upset.

i'd only met him a couple of times, but he had a real impact on my life. i think it is the passing of a great scientist. he will be truly, sorely missed. even as a young student his intelligence stood out, but atjust that moment he was given a warning that motor neurone disease would cut his life short. when i was diagnosed at 21 i was told it would kill me in two or three years. but somehow he kept going. in a high—tech wheelchair and with a synthesised voice. i am happier now than before i developed the condition. communicating first by touch, then by twitching a single muscle in his cheek — a daunting burden for anyone. his children saw him as an example. his daughter lucy spoke to us last year. people who've lived in really extreme circumstances seem to find something very, very inspirational in his example of perseverance

and persistence and his ability to rise above his suffering and still want to communicate at a higher level. life was never straightforward. his first marriage ending in divorce, as did a second marriage to one of his nurses. claims had emerged that he had been physically abused, the case was dropped for lack of evidence. none of this held him back. his book, a brief history of time, sold at least 10 million copies and everyone has wanted to meet him. from the pope in the vatican... good evening, ma'am. to the queen... nice to see you again. to barack 0bama, who awarded him a presidential medal of freedom. his fame reached far beyond the world of science. your theory of a doughnut—shaped universe is intriguing, homer. i may have to steal it. wow. even appearing in the simpsons. who's paying the tab? homer imitating hawking: i am. i didn't say that. homer imitating hawking: yes, i did! in an episode of star trek he was given the chance to tease isaac newton. not the apple story again! and is this your new friend? more recently he was happy to play

along for comic relief. astounding to think the lord created all this injust seven days. incorrect. it took 13.8 million years. let's not get bogged down in all that again! he had real a sense of adventure, even attempting a zero gravity flight. as you can imagine, i am very excited. i have been wheelchair—bound for almost four decades and the chance to float free in zero g will be wonderful. tim berners—lee, founder of the world wide web tweeted... and nasa said... if you reverse time then the universe is getting smaller. all right.

eddie redmayne played stephen hawking in the film the theory of everything and today said "we've lost a truly beautiful mind." which sums up the real stephen hawking, who could always conjur up a visionary thought. so a scientist who delved into the weird realm of black holes achieved something remarkable. he found a way of acting as a bridge between science and popular culture. he knew his work baffled a lot of people, but he hoped they'd get something out of it, understanding that there are rational laws governing the universe, and, uniquely he succeeded in reaching a global audience. professor stephen hawking, who's died at the age of 76. stephen hawking's most famous book a brief history of time has shot

to the top of the bestseller list at amazon today. he had an ability to bridge the divide between academia and popular culture. 0ur correspondent, jon kay, reflects on his enduring appeal for new generations of scientists. stephen hawking would have loved this — 20,000 young british scientists experimenting together. do it again! don't touch it. he told young people to be curious and today, as they studied trajectories and force, many were thinking of their scientific superhero. how would you describe him? genius, pioneer, brilliant, inspirational, motivationally engaging, phenomenal. i've read a brief history of time, i thought it was very interesting. did you read all of it? i did actually read all of it. and it got me into black holes and i went on to a series of lectures about them. so, yeah, it fuelled a lot for me. on display at the big bang fair, inventions

from the scientists of tomorrow. these a—level physicists, from north wales, regard professor hawking as a modern—day genius. he's the intellectual follower of einstein and newton. these amazing, amazing figures that we read about in physics books, he was getting to that level. he was incredible. his legacy will live on. for ever. see the astronaut there, look at him. inside an inflatable black hole, teenagers studied hawking's space and time theories, while taking selfies. it's a lot in one lifetime for anyone. i think he's encouraged science as a field as well. i think more people are more invested in science nowadays because of him. it would navigate you to the nearest exit. at 15, byron has invented an app which could help people escape a tower block fire using virtual reality. he admires hawking's personal courage. he was only one man who did such great things and i was really inspired by that, because usually you see people follow the same paths and try and do the same things. but stephen hawking was really unique in the sense that he wanted

to do things differently and he wanted to contribute things in a different sense. i was really inspired by that. perhaps the next stephen hawking was in this room today. jon kay, bbc news, birmingham. and after the news on bbc one there is another chance to see dara 0'briain meets stephen hawking. that's at 10.45pm tonight. students across the united states have walked out of their classrooms today to demand tighter gun safety laws. they staged a i7—minute protest to represent the 17 people who were killed in the florida school shooting exactly a month ago. here's our north america editor, jon sopel. hey—hey, ho—ho, the nra has got to go! the last time we saw children pouring out of school, it was with their hands up in terror after the florida shooting. today they came out across america, but this time with fists clenched, demanding change on gun control. what do we want?! gun control!

when do we want it?! now! in washington at ten o'clock, on a bracing cold morning, with their backs turned on the white house, these students fell silent for 17 minutes — a minute for each of the people who died at the marjory stoneman douglas school in florida last month. there's no doubting the extraordinary success these young people have had in changing the whole terms of debate on the subject of gun control in america. their problem is that the man who lives on the other side of that fence seems to have got cold feet. hey—hey, ho—ho, the nra has got to go! when donald trump met youngsters from the florida school at the white house, he seemed to offer his support for tougher gun control measures, like raising to 21 the age at which you can buy a rifle. and he later chided lawmakers for being frightened of the national rifle association. some of you people are petrified of the nra. you can't be petrified. but he's now backed off those proposals and so young people are intensifying their campaign.

we want them to pass common—sense gun laws. common—sense gun laws. we want to see a ban on assault rifles. we don't want to be scared in school. it should be our safest institution. we are tired of being scared. we want actual change. we want it to happen with this protest. this is what democracy looks like! this is a curtain raiser to a mass demonstration in washington in ten days' time. they're a long way from getting what they want, but the power of youth protest has got them further than anyone could have imagined. and they're not in any mood to surrender. never again! jon sopel, bbc news, washington. scientists have discovered tiny particles of plastic in bottled drinking water. research, commissioned byjournalists at 0rb media, studied more than 250 bottles of water, from 11 of the world's leading brands. some bottles had no particles, but others tested had hundreds

or even thousands of particles — some the width of a human hair. food safety experts say the levels of plastic found does not make the water unsafe to drink. but they are calling for more research into the effects of microplastic on the human body, as david shukman reports. they are among some of the most popular brands of water in the world, millions are sold every day, but new research has made a surprising discovery that many of the bottles contain tiny particles of plastic. and there are certain wavelengths of light that causes them to sparkle like stars in the night sky. in the largest study of its kind, bottles were water were bought in different countries around the world — china, india, brazil and many others. the project was coordinated byjournalists at 0rb media and they recorded each step of the process, from the shops, to the courier companies, as the bottles were sent to a laboratory in new york state. professor sherri mason is a chemist

specialising in plastic and she tested more than 250 of the bottles. i'm going to take a specific amount of nile red dye. the dye, nile red, has a proven ability to stick to pieces of plastic. it was first used to detect plastic in sea water. so when the bottles were emptied through a filter, what was left was a mass of tiny particles. the next stage was then to analyse them under a microscope. the dye makes anything plastic fluoresce under a particular kind of light. so the particles could be counted and some were then examined to see what they were made of. the typical microplastics that we're finding in the bottled water, at the lower end of the screen you see a fibre. this, what looks like a little hair, just there? correct. you see it in bottle after bottle and we see it in brand after brand. part of that too is, it's not about pointing fingers at particular brands, it's really showing that this is everywhere. so what exactly was found? a small minority of bottles had no

plastic particles at all. but in this video, recorded with a special light and an orange lens, you can actually see pieces of plastic. and this close—up image of a filter shows hundreds of particles, it looks like a picture of the stars. a technique developed for astronomy had to be used to count every dot. the biggest particles, larger than the width of a human hair, were confirmed as plastic, and there was an average of ten of them per litre. smaller particles were also found, an average of 314 per litre. these weren't positively identified, but were probably plastic. at the moment there are no rules covering these microplastics or any agreed way of checking for them. what's striking is how widespread this problem is. the research has studied bottles from nine different countries, 11 different brands and, in almost all of them, they found plastic floating around inside.

when they looked more closely, they found that the type of plastic is often what's used to make the cap. so the theory is, that the very act of opening a bottle, maybe what pollutes it. we approached all the companies involved, a few didn't reply. those that did said they maintained the highest standards of safety. nestle told us... it said the study "misses some crucial steps to avoid false positives, detecting something other than plastic." danone, which owns evian, said it wouldn't comment on the study because the testing methodology is unclear, and it pointed out that for microplastics there's "no regulatory framework or scientific consensus on testing for them." gerolsteiner said its own tests found microplastics "significa ntly

below the limits for particles set for pharmaceutical companies." and coca—cola, which makes dasani, said that microplastics seem to be everywhere "and therefore maybe found at minute levels, even in highly treated products." plastic is turning up in unexpected places. last year this lab found it in samples of tap water. so what does this mean for our health? right now there's no hard evidence that drinking or eating plastic particles can cause any harm, but that isn't out of the question. some of these particles are so incredibly small that they can actually make their way across the gastrointestinal track, across the lining and be carried throughout the body, and we don't know the implications of what that means on our various organs an tissues. and if there's plastic in bottled water, where else might it be? we turned to one of the british scientists who helped to develop the nile red technique for detecting plastic. this study is maybe just the start. when we start looking more carefully, we will very likely find it in food, in packaging, in milk, in any other place we look,

because i don't think mineral water is unique in that sense. despite this, the message from the scientists is clear — if your tap water is dirty, bottled water is far safer. but the world of microplastics is new and full of uncertainty, which makes research into it all the more urgent. david shukman, bbc news, in new york state. toys r us is closing all 100 of its uk stores in the next six weeks after administrators failed to find a buyer. 3,000 jobs will be lost as a result. some 25 stores have either already closed in recent days or are due to close by tomorrow. football now, and chelsea have been knocked out of the champions league by barcelona. they lost 3—0 in tonight's second leg in barcelona. joe wilson watched the action. barcelona helpfully provided a banner in english for visiting chelsea. ask anyone in the world who's football royalty, they'll answer — lionel messi.

sure, he's good, but nobody has a devine right to score. you can'tjust expect to finish your first opportunity, from an impossible angle. commentator: and he scores, messi. 0h! two minutes — messi 1, chelsea 0. even at the highest level, messi just seems superior. steal the ball, then then his legs whirl and his brain beats everyone. no shot, a pass — let dembele finish this one. commentator: he smashes it in. so chelsea were 3—1 down on aggregate, but getting a goal back seemed feasible. this free—kick brushed the post. chelsea had a lot of the ball, but messi just needed one sight of goal, aiming again for the gap between the goalkeeper‘s legs. there is a release clause in his contract. he could be yours for 700 million euros. joe wilson, bbc news.