nigeria's electoral commission has postponed the presidential poll by a week — hours before voting was due to begin. the commission chairman, yakub mahmood, says the delay was necessary to ensure a free and fair vote. the us president donald trump has declared a national emergency in an attempt to bypass congress and secure funding for his mexican border wall. democrat leaders have described it as "a gross abuse of power" and announced an immediate investigation into the declaration, which they say violates the constitution. relatives of shamima begum, the pregnant teenagerfrom london who went to syria to join the islamic state group, have asked the government to help them bring her home. britain's home secretary, sajid javid, has made it clear he'll try to prevent the return of people who've supported terrorist organisations. next week mps looking into disinformation and fake news, are expected to publish theirfinal report,

into the way our personal data has sometimes been manipulated for political influence, at the highest levels of power. and it's happening right around the world. here's our media editor, amol rajan. when you report fake news, which cnn does a lot, you are the enemy of the people. in just a few years, the phrase "fake news" has entered mainstream culture. then they've got the nerve to say we're fake news. you and your colleagues have fallen into this trap of fake news. it's a calculated and corrosive term, often deployed by those trying to discreditjournalism, but the term fake news captures an urgent issue confronting modern democracies — disinformation in the digital age. in america, authorities are investigating social media's role in russian interference in the presidential election of 2016. the nearest thing in britain is

the house of commons select committee enquiry into disinformation and fake news. over the past year, it has taken evidence from regulators, tech companies and those at the centre of allegations around the targeting of voters during the brexit referendum. the enquiry is looking at four areas in particular. first, whether social media firms are neither platforms nor publishers but a new kind of company which has legal liability for harmful or illegal content. then there's the issue of electoral law. the committee wants new rules for digital campaigns, not least around the issue of shell corporations being used to hide identities. next, what was the precise role of cambridge analytica? the committee has looked at the impact of the british data firm and has said its ceo misled them. finally, there's the kremlin question — to what extent, if any, did russia weaponise information during the brexit referendum, and why is there such a gulf between the government's warnings about security and the response of tech companies? facebook is taking disinformation more seriously and has appointed the charity full fact as its first independent

fact—checkers in britain. one thing i'm aware of is it might not be facebook in ten years‘ time, or it might notjust be facebook. we're going to need to write rules through open, democratic, transparent processes that apply to all these companies. last year, facebook was fined the maximum £500,000 by the information commissioner for serious breaches in data protection law. have you seen satisfactory evidence that they've learned and changed? i am hopeful that we'll see more of that change and i... that suggests we haven't so far. i haven't so far. i think it's yet to be seen. what do they need to do to comply with this regulatory regime which they are currently not doing? it's not good enough to say, here's what we're doing. we need a proof point and we need... facebook can't mark their own homework. social media platforms like to think they're a benefit to democracy. across the west, that's in dispute. amol rajan, bbc news. now on bbc news, it's time for our world.

more than three decades on nature has taken over. what happened to those who refuse to leave? has the truth about this place become lost in the infamy of this disaster. we are getting less of an

external dose of radiation? three times less than on the plane over. what does the future hold for those who still live in the shadow of chernobyl? 130 kilometres north of the capital, kiev, part of the country has been cut off. heading for the exclusion zone which is quite exciting. a forbidden place in shrouded in mystery. it is almost twice the size of london. we are going into the epicentre of an explosion. it happened on the 26 april 1986, dave

the would never forget. the soviet union admitted this evening that has been an accident at one of its power stations. perhaps the worst accident in the nuclear power plant industry. safety regulations mean we have to protect oui’ regulations mean we have to protect our close. if you follow all rules you do not break rules and everything will be ok. 2008 is passed after my first coming to chernobyl and everything is ok. with this is a scientist whose lives work has hinged on that terrifying night. how long have you been studying the

aftermath of what happened here? since 1990. have you been into the building before? i have never been before. reactor number four still lea ks before. reactor number four still leaks radiation so it contains remains that could blast it apart. this is the footage captured beneath that time. —— dome. it is still radioactive and people cannot be here for more than a few minutes. the plan continued to produce power until 2000 and the neighbouring react is still being decommissioned. few visitors are allowed but we have been given permission to look inside. that is my alarm going off.

we have got up to 1a, amber warning. throughout our trip, jim is measuring the radiation we are receiving. i am going to switch it off because we do not want it going all the time. there is a strange atmosphere. my heart is beating quite fast. it was 1:23am when engineers cut power to parts of the numberfour engineers cut power to parts of the number four reactor. they were testing what would happen in the event of a blackout, but they did not know was that the react was ready on stable. it wasn't as one person, it was a chain of people,

from the designers to the people operating it, to the safety culture. the shutdown slowed turbine that flowed cool water through the reactor. the reactor collapsed, everything collapsed and when this engineer pushed the button to stop the chain reaction, steam was coming from the bottom, big pressure. stea m from the bottom, big pressure. steam explosion blew the lead exposing the call to the atmosphere. the fire burnt for ten days. the initial explosion killed two people. in the days that followed, emergency workers rushed in. people known as liquidators were sent to remove highly radioactive material that had been blasted to the roots of nearby buildings could be swept up and

contained. 134 emergency workers suffered acute radiation sickness. 28th died within months, another 19 have died. some surviving workers remain scarred. the impact was not confined to this site or this country. a cloud of radioactive smoke and dust was carried on the wind around europe. information emerged only gradually from behind the iron curtain of the soviet union. that cloud though carried the truth of the disaster. the world held its breath. this was the largest accidental release of radio city in the environment in the history of nuclear power. —— radioactive material. who is to

blame, the issue is still being debated. every accident, it was concerned with human factor. if there were design faults it was a man that designed it. if it was a personnel fault, it was a man, not the robot. we came to one conclusion, it is human factor everywhere. today, the consequences of that terrible accident are etched into this region. within a boundary drawn, the primary exclusion zone. no—one was allowed to return here to live. but just beyond no—one was allowed to return here to live. butjust beyond that, captured by an out of bound boundary, a

second zone where people have been left in limbo. this town has a population of 2500. this woman runs at the kindergarten and remembers the evacuation. the future for these children and theirfamilies is the future for these children and their families is uncertain. the future for these children and theirfamilies is uncertain. the town has some of the lowest radiation levels in the zone but it is still contaminated and that means no agriculture is permitted and nothing new can be built here. the

secret for a new star, could it be hidden in the abandoned zone? to many it is a frightening place but in the decade since the accident hundreds of scientists have worked here, forensically examining the chernobyl disaster. this doctor came here in the immediate aftermath as one of the thousand of liquidators. he is now a scientist. although it is not legal to live here permanently, he works here from these previously abandoned house. this is a very organised. isn't this

a map of the exclusions and? the red are the hotspots? where is the nuclear power plant. these international community of scientists, it allows them to measure how a landscape recovers from a nuclear catastrophe. they eat, sleep and discuss their work here but the days are spent out in the field. today, with the research team, we are looking for wildlife and we eventually come across one of the many now desolate villages. it has become strangely rich habitat and a place surrogate seems totally at home. i am a feral man. sometimes i see my family not so often. this is just completely taken over.

it is why these villages have become hubs for where some of these ecological studies can be done. this is just ecological studies can be done. this isjust a ecological studies can be done. this is just a totally different place. it is not a village any more, it is a re— welded landscape. —— reap while that. inside some of these houses, it is apparentjust how quickly people had to leave. we can see someone's code. absolutely. some of what people left behind through farming and gardening have been revisions for wild animal. people, before the accident, introduced here a lot of plants. and the soil in the villages is a little bit richer than in the surrounding areas. that is why, they have started to observe

higher levels of diversity of animals. we have wolf. just outside the village there are obvious signs of animal latter moved when people moved out. you want to see wolf faeces. we have fresh wolf faeces. jim smith is with sergey to check cameras and audio recorders that have been silently monitoring the wildlife. all these years combining the tracking of animal populations and measuring the contamination suggests wildlife is now thriving on a placement he had assumed to be toxic. yes, the exclusion zone is contaminated, but if we were to put it on contaminated, but if we were to put itona contaminated, but if we were to put it on a map of radiation dose a worldwide, only the small hotspots would stand out. natural radioactivity is all around us. it varies from country to country, from place to place. and most of the area of exclusion zone gives rise to lower radiation dose rates than many

areas of natural radioactivity worldwide. it may seem strange that most of this wilderness, that was created by a nuclear disaster, had similar levels of radiation to many parts of the populated world. but being here, surrounded by nature that doesn't observe any boundaries of checkpoints, it actually feels that life is flourishing. apart from glimpses on camera traps, though, i am yet to get close to any of chernobyl‘s wildlife. doctor marina is following an unusual experiment. in1998, is following an unusual experiment. in 1998, zoologist is released ahead of endangered wild horses here in the hope they would greater weight over growth and reduce the risk of fire. marina has just over growth and reduce the risk of fire. marina hasjust spotted over growth and reduce the risk of fire. marina has just spotted a whole herd of these horses. let us

see if we can get a little bit closer. so they have adult females, several cubs. several babies. some of them are one years old, some of them are two years old. these animals are native to be open plains of mongolia, but marina's workers revealing some unexpected behaviour that allows them to thrive here. they use the abandoned buildings, because they are avoiding mosquitoes and heat and wind inside. so they are adapting to the exclusion zone? they are sleeping inside. so they have really well adapted to this place. they are really using the buildings. amazing. wildlife may be

making the most obvious place, but not every village was left for to reclaim. we are deep in the permanently abandoned zone. and some people still live here. victoria. nice to meet you. today it is maria's 78th birthday and she has made us breakfast. thank you. after the day of the accident, this had been the only home she knew. her family then travelled back across a patchily reinforced boundary. they refused to abandon the place. maria and her neighbours make up the

remote community of just 15. maria and her neighbours make up the remote community ofjust15. a tiny village reclaimed after the disaster. the residents of this village are amongstjust 200 the residents of this village are amongst just 200 cell settlers the residents of this village are amongstjust 200 cell settlers who returned and it stayed. —— cell settlers. the vast majority who lost their homes in the exclusion zone have no hopes of ever coming back. almost 50,000 of them lived here in that pripyat. —— lived here in

pripyat. this was the soviet drinker, purpose built for workers at the power plant. it was evacuated overnight —— dream town. no residents were allowed to return. just a few kilometres from the plant, this is one of the hotspots. and after the city was permanently abandoned it gradually turned to ruin. but in recent years, human activity has come back. pripyat has been deemed safe to visit for short periods and is now a tourist destination. 60,000 people came here last year, keen to witness the decay. chernobyl was number one on the list. it was something in the news a lot when i was growing up as a kid. so it took on the imagination. i wanted to see what it was like. it is sort of the post- apocalyptic environment, which, i think, is very scary. the sense of danger here is now a

selling point. but should we fear this place? that is a question only be decades of research can answer. on the dry bed of what was the reservoir providing water to cool the nuclear reactors, we have come withjim to the nuclear reactors, we have come with jim to meet the nuclear reactors, we have come withjim to meet this team. the nuclear reactors, we have come with jim to meet this team. we were just fly with the helicopter to look at the plant area, collecting samples of water, soil. he first came herejust samples of water, soil. he first came here just three samples of water, soil. he first came herejust three months samples of water, soil. he first came here just three months after the accident. his work helped shape the accident. his work helped shape the exclusion zone. this is more than half of my life. in the early stage of the accident, the most important was to understand what is the extent. to drop the first map. to draw up the first maps, yes. then, of course, much later, as we know, the contamination is

significantly different all over this area, yes. and in this spot, with the help ofjim, it is clear just how much the contamination varies and how much this place has changed. so here, standing essentially in the cooling pond of the nuclear power plant, a kilometre from where the nuclear accident happened, we are getting less evaders. retre is less than what we got on the aeroplane coming over. what could that mean for the outer zone? this is a community on the brink of change. the objective is to support and pray... jim and his collea g u es support and pray... jim and his colleagues are here for a meeting that could remove this district from the exclusion zone. meaning they could start farming and building again. all of the stakeholders here

are representatives of the local community, the administration, those who run the exclusion zone, hopefully that agreement will come about you today. many here still fear chernobyl radiation, how it might affect their and their children's health. might affect their and their child ren‘s health. long—term impacts, though, have been hugely collocated to armpit. estimates of cancers directly caused by the radiation range from a few hundred cases to many thousands ——an epic. the contamination is not worth caused by a thousand people, who we re caused by a thousand people, who were children at the time, to develop thyroid cancer. the vast majority were treated and cure. there were numerous reports of birth defects and other health problems, it is just not clear if any were linked to radiation. what is conclusion that make conclusive, according to the world health organization, is that people's mental health has been damaged by fear of radiation and the disruption to their lives. this meeting could lift restrictions that this

community has lived with ever since the accident. how did today go, do you think? we are certainly in agreement here that there needs to be change. so the next step is to communicate with the politicians, tell them what our scientific conclusions are, tell them what the district want, and we hope they will ta ke district want, and we hope they will take action. what is finally on the horizon is that these children may no longer be the children of chernobyl. if that political agreement can be reached, the next generation here could shape its own future. that disaster still casts a long

shadow here and what happened in 1986 will always be a feature of this place, but the research that has been carried out here shows that over 30 years the situation has changed and now, perhaps, for the sake of people who live here, it is time to move forward. hello. where we have seen most of the sunshine of the past couple of days there will be more cloud around, at least to start the weekend. here is how saturday is shaping up. there will be patchy rain at times through northern and western parts of scotland. on the

whole, dry weather around. a lot of cloud across southern england, advancing across wales, the midlands, into east anglia as the day goes on. could be parts of eastern scotland, north—east england that see some of the best sunshine and the highest temperatures up to 15 celsius in the warmest places. a lot of this cloud will clear away as we go through saturday night. we are going to see some rain putting into northern ireland and at times into north of scotland. no frost as we start off on sunday. sunnier skies for many of us, but this area of cloud and occasional rain will work in from the west, clearing to northern ireland as the sun comes back, the rain heavies signalfor scotland. not much reaching eastern areas. more cloud putting in late in the gate after the sunshine. —— pushing an late in the day. this is bbc world news, i'm reged ahmad. our top stories: hours before voting was due to begin, nigeria's presidential election is postponed for a week.

donald trump invokes national emergency powers to fund the border wall with mexico. his opponents are furious. we are going to confront the national security crisis on our southern border, and we are going to do it one way or the other, we have to do it. the family of the pregnant teenager who joined the islamic state group pleads with the british authorities to help bring her home. and, junk in space: engineers test a new satellite harpoon—system for collecting floating trash.