welcome to bbc news, broadcasting to viewers in north america and around the globe. my name is nkem ifejika. our top stories: the usjoins britain in blaming russia for last week's nerve agent attack. at the united nations, its ambassador demands action. the credibility of this council will not survive if we fail to hold russia accountable. moscow again denies any involvement in the attack. translation: we demand that material proof be provided over the allegedly found russian trace in this high—resonance event. a month after the floida school shooting, students across the us walk out of their classrooms to demand tighter gun controls. and ten plastic particles per litre, growing concerns over many brands of bottled water. hello and welcome to the programme.

the white house has backed britain's decision to expel russian diplomats in retaliation for the nerve agent attack on sergei skipral and his daughter. the us said it was a just response and america stood in solidarity with its closest ally. 23 staff at the russian embassy in london have been given a week to leave the uk. but the kremlin continues to deny any involvement in the attempted murder. 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. is this represents an 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 the 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. blade anger displayed in westminster that this is happening in british streets. —— anger displayed. 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. at the united nations, america, germany, france, canada and australia

all offered support to britain. france is saying it wants to see firm proof of russian involvement before deciding on any course of action. here's the uk's deputy ambassador to the un, jonathan allen. a weapon so horrific that it is banned from use in war was used in a peaceful city in my country. this was a reckless act, carried out by people who disregard the sanctity of human life, who are indifferent to whether innocents are caught up in their attacks. they either did not care that the weapon used would be traced back to them, or mistakenly believed that they could cover their traces. russian officials and media channels have repeatedly threatened those they consider traitors, even after the 4 march attack. that prompted a lengthy reply from the russian ambassador. here's part of it. translation: we were given an ultimatum and required — requested in 2a hours to admit that we committed a crime. in other words, confess. we do not speak the language of ultimatums, we do not use that language with anyone,

and we will not allow to be spoken to in that language either. we demand that material proof be provided over the allegedly found russian trace in this high—resonance event. moscow has accused the uk of a flagrant attempt to mislead the international community, denouncing the diplomativ expulsions as unacceptable, unjustified and short—sighted. our correspondent, steve rosenberg, has the view from the russian capital. 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's 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 ofcom 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‘s 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, the territory vladimir putin annexed from ukraine. 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. and there's plenty more analysis

on our website of the uk's decision to expel 23 russian diplomats and russia's dismissals of the allegations. you'll also find an explanation of what novichok nerve agents are. that's all at bbc.com/news. tens of thousands of students have walked out of classrooms across the united states to call for tighter gun controls. 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. all chant: 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?! all chant: gun control! when do we want it?! all chant: now! in washington at 10am 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. cheering and applause 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. all chant: 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 2! 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 the young people are intensifying their campaign. we want them to pass common—sense gun laws. common—sense gun reform. we want to ban assault rifles. background checks, everything.

we don't want to be scared in school. it should be our safest institution. we're tired of being scared. we want actual change. we want it to happen with this protest. all: 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've imagined. and they're not in any mood to surrender. all chant: never again! jon sopel, bbc news, washington. on the line is sabrina mahmoodi, a high school senior who helped organise the walkout at bentonville high school in arkansas. sabrina, thank you forjoining us. i wanted to ask you, your state, arkansas, is necessarily one in favour of more gun controls. so you don't necessarily represent your

stake in going out and protesting for more of these? that would be a correct assessment. i'm the president of the young democrats at bentonville high school, so we are a minority in our state, but what we've stressed about the walkout is that it we've stressed about the walkout is thatitis we've stressed about the walkout is that it is a bipartisan demonstration. we're trying to dispel the myth that you cannot be pro— second amendment and pro— comprehensive gun reform. we are trying to really educate our community on what the second amendment means and how we can put it into a more modern context by allowing more regulation of it. but that's precisely what many people, for example, the nra, do not want. if you look at the marjory stoneman douglas case, there were lots of lapses with regard to the fbi missing out on cues, and the

argument has been won that this was not necessarily about access to guns, it was that the flags that we re guns, it was that the flags that were raised were not looked at, were not attended to? that's definitely an argument that's being pushed by the nra and we do think it does have merits, we do have a mental health problem in our country, however, mental health is notjust an american problem, it is a global issue. but gun violence is very u nfortu nately clearly a n issue. but gun violence is very unfortunately clearly an american problem. we see developed nations in the amount of incidence of gun violence in the world and that's not a statistic we want to be a part of. we recognise the nra does not... is wa ry we recognise the nra does not... is wary of any types of regulations in regards to the second amendment.

however, we realise, you also have to consider, although they are a lobbying group, lobbying groups are supposed to represent those groups who really believe in what, you know, the group believes, however we believe as students, as children, as really growing members of this society, we deserve a safer, more secure educational environment and children should become before weapons. sabrina mahmoodi, a senior at bentonville high school in the state of arkansas. stay with us on bbc news. still to come: inspired by science and stephen hawking. a curious generation pays tribute. today we have closed the book on apartheid and that chapter. more than 3,000 subway passengers were affected. nausea, fainting, headaches and the dimming of vision, all of this caused by an apparently organised attack.

the trophy itself was on the pedestal in the middle of the cabinet here. it was an international trophy and we understand now that the search for it has become an international search. above all, this was a chance for the christian democrats of the west, offering reunification as quickly as possible, and that's what the voters wanted. push this is bbc news. the latest headlines: the us says it agrees with britain, that russia was behind the nerve agent attack that poisoned a former

spy and his daughter on uk soil. russia has dismissed the allegation. let's get more on the uk's plans to plans to deport russian officials over the poisoning of a former spy and his daughter on uk soil. dr michael carpenter is a former us deputy assistant secretary of defence with responsibility for russia and was also director for russia at the national security council. i asked him what impact such expulsions can have. i think it's going to have very limited impact. a persona non grata declaration or expulsion of diplomats is largely a symbolic move and doesn't have many long—term consequences for russia. this is something we debated in the united states after we expelled 35 russian diplomats who we thought were spies from the embassy here. the lasting consequences were really nil. what can nationas like the uk and france and parts of europe that have been in the sights of russia,

what can they do to have an impact, something which russia will feel? the most concrete thing is increased sanctions. you have to understand, so far, the sanctions that have been are rather weak. some limited debt equity restrictions on financial institutions. we have gone after upstream energy production and defence firms but we haven't applied the sanctions we have as we have in the case of iran in north korea, called full blocking sanctions. sanctions that prevent a financial institution or bank from doing any business at all. if we did that to two or three of the top ten russian banks, it would have an immediate impact. moscow would notice. one of the things russia can do straightaway is restrict gas flow to countries in eastern europe. winter is not quite gone yet. if you poke the bear, the bear will fight back.

in terms of gas flows, it's a 2—way street. russia depends on gas revenue from western europe. we've seen them threaten ukraine, it has been able to reroute deliveries through other western european countries. gas, more and more. europe depends on piped gas from russia but more and more, that threat is empty. the last question, why is it whenever these kind of things happen, the uk or the us suddenly finds these russian spies. it's almost as if they never knew about them but they did know about them, so why expel them now? that is a good point. the uk has known about these 23 individuals. the united states, we knew about the 35 we expelled. frankly, we should have taken action earlier. in our case, we prevented the russians from using diplomatic facilities we knew were used

for espionage so there are some overdue steps which are finally happening. a conservative tv commentator, larry kudlow, has accepted president trump's offer to make him his new top economic advisor. the former investment banker, who works for cnbc, will replace gary cohn, who resigned last week over the introduction of new steel and aluminium tariffs. he was an early supporter of mr trump, but has often criticised the white house for its attacks on free trade. researchers in the united states say they've found particles of plastic in some of the most popular brands of bottled water. in the largest study of its kind, more 200 bottles were put through a screening process. it should be pointed out though, that food safety experts say the levels of plastic found, does not make the water unsafe to drink. but they're calling for more research — as david shukman reports. bottles of water are feature of everyday life around the world. new tests commissioned byjournalists at 0rb media have discovered something unexpected, tiny particles of plastic in the water. at this laboratory in new york

state, tests were carried out on over 250 bottles. a special kind of dye was added that's known to stick to pieces of plastic. under certain wavelengths of light they sparkle like stars in the night sky. on an average per litre there were ten large particles, each larger than the width of a typical human hair and confirmed as being plastic. smaller particles were also found. on average, 314 per litre. they weren't confirmed but were probably plastic. at the moment there are no rules covering these microplastics or any agreed way of checking for them. it's an indication that we should be concerned. it's not catastrophic, these numbers we're seeing, but it is concerning. especially if you look at them, if you're drinking only bottled water and do this every day over a year, you know, you are literally talking thousands of pieces of plastic that you are ingesting just

from the water you were drinking. we contacted all the companies involved. nestle told us that today they have not found microplastic compounds beyond the trace level in their product. danone, which owns evian, said of the study that the methodology is unclear. and that there were no rules on microplastics. coca—cola, that makes dasani, said the micro plastics seem to be everywhere and may be found at minute levels, even in highly treated products. this is the first time that bottled water has been tested for plastic on this scale. 11 different brands bought in 19 countries. and in almost every case, researchers have found plastic. what does this mean for our health? the food standards agency says it is unlikely the microplastics could cause harm. but the world health organization now wants to review the evidence and scientists say more

research is needed. as we become more aware of the prevalence of microplastics, and the potential harm that they might cause, i think we need to start thinking now about how we can reduce those imputs so we're not stoking up a huge problem for the future. the advice, where water supplies are dirty, is that bottled water is far safer. but this study does raise questions about where plastic can end up, and whether the tiniest pieces can affect our health. david shukman, bbc news, in new york state. a growing number of women—only shared work spaces have been opening up in the us and europe. this comes as the treatment of women at work has been in the spotlight, with more debate about how to prevent sexual harassment. we visited one all female co—working space in new york to learn more. the world is a boys club. there have

been men's clubs in men's only places for centuries and that's where business deals gets made and decisions are hatched. women deserve spaces like that too and that's what we've created here. the wing is a women's only co—worker in space. at night, it transitions to a social club. the thing that we heard from a lot of our friends who had experience of co— working spaces is that they didn't have the amenities that they needed as women so there were pumps for beer but not for breastmilk. i'm a full—time entrepreneur and in my early stages of the company, i was working out of coffee shops. men would often come up to me and try to hit on me, interrupt my work, even though i would have my head down, clearly trying to work. i would deal with, honestly, rampant harassment. working in a female only co— working environment is like coming to a safe haven. the me too movement,

time up, broad conversations around harassment and safe workplaces. for us, it's really reaffirmed the need for female spaces like the wing. scientists have been celebrating the work of professor stephen hawking, the world—renowned physicist who has died at the age of 76. 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. 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. 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. the us agrees of britain that russia was behind a nerve agent attack that poisoned a spy and his daughter on uk soil. moscow's ambassador to the un denied russian

involvement in the attack. you can get in touch with me and most of the team on twitter. i'm @nkem|fejika. hello there. 11! degrees yesterday in london. 40mm of rain in northern ireland. those were the contrasts we had. together with the rain in the west, we also had some quite strong winds as well. now, the rain is going to be moving, it starts as rain over the next few days but then it turns colder. we get an easterly wind just in time for the weekend. that's when it really feels cold. we may get some snow showers, mainly for england and wales. this is where we are, though, at the moment. this weather front here is moving its way a bit further north and east across the uk. stronger winds ahead of that weather front, lighter winds developing further south, and we should get some sunshine as well. still some rain, though, for northern ireland on thursday morning and that moves through the midlands away from the south—east of england, heading towards southern scotland and northern england. sunshine to the south

and we get some sharp showers. possibly thundery. 12 or 13 degrees. north of that band of rain it is quite a bit colder, but the cold air is yet to arrive. we'll see that rain turn to sleet and snow over the higher ground overnight in scotland. still some rain for the north—east of england and we could still see some sharp bands of showers pushing up across england and wales towards northern ireland. again, no frost i think early on friday morning. that wet weather in scotland increasingly wintry over the high ground. some heavy, perhaps thundery showers in a band moving across northern england, running into the back of that wet weather and bringing more rain to northern ireland. heavy showers again developing to the south where we'll get sunshine. contrasting temperatures again north and south across the uk. over the weekend, we all get into the same boat. high pressure blocking things off across scandinavia and around it we pick up an easterly wind. there will be a significant windchill as well, especially across england and wales, where we'll have the strongest of the wind. perhaps not too many snow showers, actually, on saturday. there could be some on friday night, but most places will be

dry on saturday. you will notice, however, remember 12 or 13, perhaps, across the south on friday. four or five at best, and further north one or two celsius. that area of high pressure still around the northern part of the uk on saturday. stronger winds to the south. we could get as spell of snow overnight and especially near channel, the southernmost counties of england. that pulls through and then we'll probably find a few more snow showers, again more likely across england and wales. most of scotland and northern ireland will be dry and it is not quite as windy here but it's still going to be cold on sunday, colder than it should be. this is bbc news, the headlines: the us says it agrees with britain that russia was behind the nerve

agent attack that poisoned a former spy and his daughter on uk soil. moscow's ambassador to the un denied russian involvement in the attack. earlier, britain announced the expulsion of 23 russian diplomats. tens of thousands of students have walked out of classrooms across the united states to call for tighter gun controls. they staged a i7—minute protest to represent the 17 people who were killed in the florida school shooting exactly a month ago. researchers in the united states say they have found particles of plastic in some of the most popular brands of bottled water. in the largest study of its kind, more than 200 bottles were screened. an average of ten plastic particles per litre were discovered, each larger than the width of a human hair. now on bbc news, click. this week: