Nasas cassini gets closer than ever before to the planet. Coming up in the sport on bbc news, in age, theres14 years between them, but today, Anthony Joshua and Wladimir Klitschko came face to face ahead of their world title fight. Good evening and welcome to the bbc news at six. Another terror alert just yards away from last months deadly attack in westminster. Armed police have arrested a man under the Terrorism Act and seized knives he was carrying. Its now clear that the suspect who was captured on whitehall was under surveillance by Scotland Yards anti terror squad. Asjune kelly reports, theres been a High Profile Police presence in the area since Khaled Massood killed five people, including pc keith palmer, in march. Under arrest in the shadow of Government Buildings in whitehall. The man was detained by armed officers Near Parliament square. This was not a random stop search and arrest. It is understand the man was targeted by police as part of an operation by Scotland Yard counterterrorism command. It was just before 2 30pm officers moved in on him. This is what he left behind, a rucksack and his knives. Police are said to have wrestled the suspect to the ground. It is close to the Foreign Office and the entrance to Downing Street. There was something happening in Parliament Square and i walked quickly here. It was cordoned off. I spotted a suspect. He was literally next to the telephone box. He was cornered by armed police officers. The Prime Minister was away from london on an election visit to derbyshire. Im aware a man has been arrested in whitehall and that individual has been arrested on the basis of a terrorism charge. I cannot say much more about it because it is an Ongoing Police investigation, but i think it shows oui investigation, but i think it shows our police and intelligence and Security Services are on the alert as always, looking to keep us safe and secure. For the second time in just over a Month Westminster was once again on a terror alert, but this time to the relief of those who work here and many visitors, any threat was stopped. No one was harmed. The suspect is said to have no link to khaled massoud, who launched his murderous assault with a carand then launched his murderous assault with a car and then a knife. He was shot dead by police. He took the lives of five people, including pc keith palmer, who confronted him inside the grounds of parliament. Since then there has been a heightened sense of security. The fact he is in a location recently the subject of an attack would make any investigating officer to think this is the time we step in before he causes harm. The fact he was making his way towards parliament is a key point, that they would want to take him out when he least expected it. The man is said to be 27 and from london. It is understood he holds a british passport, but was not ordered the uk. Counterterrorism detectives and mi5 will have built a picture of him as they monitored his movements. They will look at his mental state, beliefs and associates. Danjohnson is there for us. I know you have been there a while, what have people been saying about this . You can see how close we are to parliament and the same distance from the gates of Downing Street. People who were here were drawn back to thinking of the Terror Attack a month ago. The arrest was made on the island in the Middle Of The Road and people described how afraid they we re and people described how afraid they were when they saw armed police draw weapons and make the arrests. They saw the weapons on the ground, these knives. One man told me he counted at least five knives laid out on the street. There was a Police Operation that blocked whitehall for a couple of hours and things are returning to normal now after forensics investigators completed their work. People were afraid by what they saw and there is a sigh of relief it was not more serious. It appears the Police Stepped in effectively and quickly to deal with this. With me is our security correspondent gordon corera. This man was clearly on the Security Services radar. This was not a random stop, it is what is described as an Intelligence Led operation and iam as an Intelligence Led operation and i am told he was on the radar of the counterterrorist police and Security Services who had concerns. It may have been the case, although it is not confirmed, that he was under surveillance at the time and as they saw him move to westminster, where there had been an attack, they decided to act. What does it tell us . On the threat, police said they do not have evidence of an immediate ongoing threat, after this arrest, which seems to indicate they think he was acting alone, but the threat level is that severe, meaning an attack is highly likely. I think it is the kind of incident we saw at westminster, with khaled massoud, the thing police are worried about. Police and mi5 are working on this threat and in this case they did exactly what you would hope, which is to have an individual they have concerns over under surveillance and move against them if they consider there is a threat to life. Boris johnson weighed into the Election Campaign for the first time today and immediately ran into some political flak. He told the bbc that if asked britain would take part in further American Action in syria even without a vote in the house of commons. Labour have also criticised what they say is a highly personalised attack onJeremy Corbyn. Our Political Editor Laura Kuenssberg has been speaking to both men. Coffee fuels campaigns. So do big personalities and they do start early. Boris johnson burst out this morning. It seems incredible when you have a threat. With both barrels, claiming Jeremy Corbyn is wea k barrels, claiming Jeremy Corbyn is weak on defence and cannot be trusted. And suggesting the uk could join in, if america again bombed syria. If they come to us and ask for our support, with whatever it happens to be, as is the case in 2013, john, in my view, and i know it is the view of the Prime Minister, it would be difficult to say no. You would have to go to the commons. That needs to be tested. You will not sure . It would be difficult for us to say no. He said similar before, but it matters now because the tories believeJeremy Corbyn is soft on defence, whether regarding syria or the rest of the world. There is a risk that people will say, he is just world. There is a risk that people will say, he isjust down islington herbivore, a muddleheaded. Will say, he isjust down islington herbivore, a muddleheaded. M seems all the tory party will do is be rude aboutJeremy Corbyn . Seems all the tory party will do is be rude about Jeremy Corbyn . The world is more unstable and uncertain than perhaps we thought it would be 20 years ago, and that is why theresa mays leadership now is important and why it is important to draw the contrast between her approach am what i think would be the chaotic approach underJeremy Corbyn. Jeremy corbyn is in their sights. You could call him the underdog. In a park today in the marginal seat of harlow. But labour mps fear their leader has to be reminded notjust to talk to his true believers, but to the whole country. The tories think that makes him a real outsider. We take a message to the country. Politics is of course always personal, but so far this of course always personal, but so farthis campaign of course always personal, but so far this campaign has been much more about tory attacks on Jeremy Corbyn than a big battle of ideas. What you think about what the tories have been doing . It is personal. That is their nature, David Cameron was a bully and they are proving to be bullies. It seems like a witchhunt. It does seem like a hunt. Why doesnt borisjohnson it does seem like a hunt. Why doesnt Boris Johnson Talk About Tory Policies for the General Election and not have a go at the Labour Leader . His wife seems to wa nt to Labour Leader . His wife seems to want to avoid the attention. This is an awkward moment for labour. Are you worried it is turning into a Personality Contest . It is what the tories trying to do, make it about you. I do not do personal abuse, i dont do name calling, i dont believe in that kind of politics. We are sent to parliament to represent people and put forward a serious debate and that is what we will do. If you were Prime Minister and the president of america asked the uk to support them in a strike on syria, what would you do . Call the Secretary General of the United Nations. We need enhanced pressure to get political settlement in syria. Raising potential Military Action against syria is controversial in any campaign. The other parties were not impressed. Unilateral, illegal intervention would be counter productive and it seems borisjohnson would be counter productive and it seems Boris Johnson is would be counter productive and it seems borisjohnson is following tony blair in that respect. If the government wants Parliamentary Authority they should ask for it, not speculate why do and jumped what President Trump does. The Prime Minister would not go as far as foreign secretary. But she and he believe Jeremy Corbyn foreign secretary. But she and he believeJeremy Corbyn is vulnerable. And they plan to make it hurt. Brexit is a key issue in this election and today the german chancellor Angela Merkel has been speaking about what kind of deal britain might expect. She told the German Parliament that some people had what she called illusions that britain outside the eu could enjoy the same privileges that it currently has inside the union. Lets hear what she said. Translation unfortunately, i have to say clearly that i have the feeling some people in Great Britain Chancellor Merkel was speaking in berlin as ministers from the eus remaining 27 countries met in luxemburg to finalise in luxembourg to finalise their Negotiating Stance on brexit. In a moment, well have laura kuennsberg, but first, Damian Grammaticas at the eu meeting in luxemburg. At the eu meeting in luxembourg. You might tell us what Angela Merkel said and what we make of it. |j you might tell us what Angela Merkel said and what we make of it. I think what Angela Merkel sought to do, addressing her parliament, was to introduce some hard headed clarity about what the eu side is prepared to agree to and also show a flash of frustration. She said a country that leaves the eu, when it is outside the Single Market and customs union, cannot enjoy the same benefits as it does as a member of the club. She said that was self evident and she thought to try to argue about that was a waste of time. They are worried about the messages they believe are being sent in the uk that a deal could be achieved by a leader taking a tough approach with the eu, and also worried i think about the impact on negotiations. Interestingly, that was reflected here today by the Vice President of the commission, deputy to jean claude juncker, who was the commission, deputy to jean claudejuncker, who was here for the ministers meeting, and he told me whatever happens in the uk election, will have little or no bearing on the sort of deal the eu will be prepared to do with the uk. A bigger mandate he said would not meana a bigger mandate he said would not mean a better deal and the use id say they are now ready for those talks. Laura, theresa mays pitch in the election is she is best placed to negotiate brexit. What is her reaction . In the next few minutes, addressing a crowd of the Party Faithful in yorkshire, she will take these remarks head on, even mentioning Angela Merkel by name, and saying 27 other countries are lining up to oppose the uk. How rivals might try to claim finally the tory Prime Minister is undergoing a Reality Check of how difficult life will be in terms of getting a brexit deal, but for the Prime Minister this is convenient. On day one of the Election Campaign one of her central reasons for calling the election was because brexit will be such a difficult process , brexit will be such a difficult process, that she needs every vote she can to strengthen her hand, a phrase we have heard time and again, she wants her own mandate is to get brexit done. So building up an image where brexit will be fiendishly complicated and difficult will be used by the Prime Minister to try to painta used by the Prime Minister to try to paint a picture only she and she alone has the authority to get it done. Of course, that will be challenged by her rivals every step of the way. Our top story this evening. Another terror alert in westminster a man has been arrested by armed police near Downing Street. And still to come why were switching back to paper and turning off our e books. Coming up in sportsday on bbc news it might not be a Title Decider but a place in the top four is still hugely important for Manchester City and Manchester United ahead of tonights big derby. Children and young people feel social media sites are not doing enough to protect them from inappropriate imagery and bullying content. The nspcc said four out of five youngsters felt sites like facebook and askfm were not shielding them. Felix alexander was a victim of online bullying. Exactly a year ago the 17 year old, who was victimised at school, took his own life. Our media editor, amol rajan, has been speaking to Felix Alexanders mother, lucy. When social media kicked in about the age of 13 or 1a became something he couldnt escape from. It became people he didnt even know would be messaging him, telling him he was hated, he wasnt welcome. 17 year old Felix Alexander seemed a teenager like any other, with plenty of friends and a love of sport. But there was a much darker side to his life. Years of abuse online destroyed his self confidence. One year ago today, he took his own life by stepping in front of the train. His mother says that with modern social media, there is no respite from bullies. Everything is very instantaneous, everything has to have a reaction immediately, and they look for that the whole time so it becomes all encompassing. It becomes completely overwhelming. Even if i took felixs phone away, he would come down in the middle of the night to try to find it just to see what people were saying. It becomes just this thing that takes over your entire life and you cant see further than that. Lucy alexander is now working with schools across her home city of worcester to warn pupils about bullying on social media. Online abuse is invading and destroying lives across the country. But tackling it goes to the heart of the debate about the role and responsibilities of internet companies. Is it up to Big Technology firms to clamp down on abuse . Or do we need new and smarter regulations . Many high profile celebrities have become advocates of reform, having endured abuse themselves. They include former footballer gary lineker. In many ways, whether it be facebook, whether it be twitter, or whether it be the other things that are around these days, i think it should be their responsibility and i think they need to make greater efforts to stop the kind of abuse, to stop the kind of bullying that can have. Yes, i can deal with it but a lot of people cant. The Mental Health of teenagers is a growing concern for the health secretary. He says Tech Companies need to do much more. What Technology Companies cant do is just sit on the sidelines and say, this is nothing to do with us, we are just the medium through which people communicate, we have absolutely no responsibility. And for people who are underage, i dont think its unreasonable to ask Tech Companies to help us sort out this problem. They should be part of the solution, at the moment they are the problem. Jeremy hunt accepts the government also has a role. For their part, Tech Companies argue theyve taken Decisive Action already. Twitter say they are providing users with new tools to block or mute abuse, safer search results, and that theyre stopping the creation of new abuse accounts. Whats the age gap between felix and his next sibling . Four years. As Lucy Alexander marks a First Anniversary few parents can imagine, the question of who will take responsibility for cleaning up social media remains open. Amol rajan, bbc news. Crime recorded by the police in england and wales went up by 9 last year with increases across almost every category. Violent offences went up by 19 and there were also rises in knife crime and buglary. In knife crime and burglary. But the office for National Statistics claimed much of the overall increase was due to changes in the way Police Record offences. An inquestjury has concluded that gross failures in the care given to a mother suffering from a rare post natal psychosis in a london hospital, contributed to her death. Alice gibson watt, a jewellery expert whod appeared on the bbcs antiques road show, suffered a severe psychotic episode, four weeks after giving birth in 2012. She was admitted to a Mental Health unit, where she suffered a Cardiac Arrest and later died. Royal marine alexander blackman, who had his sentenced reduced for killing a wounded taliban fighter in afghanistan, will be released from prison tomorrow, say his supporters. Sergeant blackman, known as marine a during the case, had his Murder Conviction quashed on appeal last month and replaced with manslaughter. Police have written to politicans in scotland giving them advice on how to handle suspicious packages. It follows incidents when packages containing white powder were sent to an elected official, the headquarters of a Political Party and a council building. According to officials at the scottish parliament, all three packages were associated in some way withjunes General Election. Government plans to tackle Air Pollution will now have to be published before the General Election, following a ruling at the high court. Ministers had argued that publishing the document would break rules on official policy announcements during the lead up to polling day. In the ruling, the threat from Air Pollution was described by the judge as real and persisting. Our Science Editor David Shukman reports. Heavy traffic outside the high court as the government, once again, faced questions about Air Pollution. This time, because of another delay in releasing its plans. An environmental group, client earth, was there to argue that ministers should speed up. The government case is that an election rule, called purdah, prevents them doing that. In hisjudgement, Mrjustice Garnham said that purdah was not a reason for delay. It is not a trump card to be deployed at will, he said. He described the dangers of nitrogen dioxide, a key pollutant, the threat is real and persisting. The government told the court that it was ready to publish its clean air plan, but couldnt because of the convention known as purdah, restricting the release of major new policies during an Election Campaign, but the judge didnt accept that. He said the governments own figures showed as many as 64 people were dying prematurely every day because of dirty air. So, whats the next step in this battle over Air Pollution . Well, the judgment orders the government to publish its new plan right after the local elections next month. Its a sensitive time. Well, i think its very important for everyone to understand that this isnt a political decision and that cleaning up the air isnt a matter of politics. What thejudge said, very, very clearly is when you have a legal obligation, and a court order, to do something as important as protect the public health, by cleaning up the air, politics does not come into it. The government is considering whether to appeal. Whatever it does, the courts ruling will eventually have an impact on millions of drivers, as new measures to tackle pollution come a little closer. David shukman, bbc news, at the high court. Travelling at 70,000 miles an hour, the cassini space probe has been exploring the Planet Saturn and its famous rings for years. Now it has just completed its first perilous dive between the rings and saturns cloud tops to find out more. At Mission Control in california, celebrations as scientists find out that the manouevre had worked. And these are the new images the spacecraft has sent back nearly three quarters of a billion miles away. This shows a huge storm raging on saturn, along with Drifting Clouds in its atmosphere. Cassini will make further plunges over the next few months before burning up in saturns atmosphere. Books are back. Well, at least according to new figures which show 2016 was a record yearfor book sales. Our correspondent Rory Cellan Jones has the story. These devices seemed to promise the same kind of people that we have seenin same kind of people that we have seen in the music industry, but many have decided they preferred to read it, good Old Fashioned have decided they preferred to read it, good Old Fashioned printed page. See . The tiger who came to tea. Elaine davis likes to take her grandson harry to the book shop most days for his benefit, as well as hers. What is your attitude to reading real books as opposed to electronic books . They are different and i read them at different times, but i love real books. I love the feel of the books, i love to see the book sitting there. I like books around the house. And elaine isnt alone. A record Yearfor Uk Publishing has seen a surge in sales of printed, not digital, books. Last year, sales of physical books rose by 8 . But total digital book sales fell by 3 , and sales of consumer e books, the bestsellers youd find in most book shops, went down 16 . Devices like the kindle promised to spark an upheaval in the book trade, with a generation getting used to reading on screens. But now that revolution appears to have stalled. In every aspect of our lives we have screens in front of us, whether it be work or home, and people are choosing to spend time away from them. People are choosing to spend time in their leisure moments looking at a book, a printed version. Harry potter and the cursed child was the bestselling book of 2016. Overall, childrens books were the star performers for uk publishers at home and abroad. Grannies, granddads, aunties, uncles are buying books as presents for children to encourage them. Teachers are. The chris evans writing competition. I think all those those kinds of things are promoting reading and literacy and the importance of books and a good story. Audio books are increasingly popular and academic books on moving online. But it seems the long history of the printed book still has a future left. Rory cellan jones, bbc news. Time for a look at the weather. Heres louise lear. A good book and a roaring fire has been needed this week. Today, a different story, lots of sunshine coming through st andrews and we have seen 15 degrees in parts of the south east. We have had a few april showers across Eastern England and this has been the story on and off today across parts of east anglia and cambridge in particular. The showers still to clear, they will gradually drift away south and west through the evening overnight tonight, but acting like a cloud of blanket really, preventing the temperatures from falling away. It is not going to be as cold night as the ones just passed and it should be frost free for many. We start off tomorrow morning, the eastern half of the country with the best of the weather. Spots of rain and scattered showers likely to crop up across Western Areas as we go through the day but its a relatively straightforward quiet friday for money. We will see temperatures peaking at eight 13 degrees. The start of the Bank Holiday Weekend looks promising, probably the best day of the extended weekend, just a scattering of isolated showers and winced irving to a southerly. Theres a level of uncertainty by the end of saturday into sunday, an area of low pressure. It wouldnt be area of low pressure. It wouldnt be a bank holiday without the threat of some rain, and it wouldnt be a bank holiday without some uncertainty as to where that rain be sitting. Keep watching the forecast, the position of that could potentially change, but at the moment further north and east doesnt look too bad. So it will be breezy but a milder Bank Holiday Weekend and they will be some rain on the cards, but it is not all doom and gloom. That is all from the news at six. It is goodbye from the news at six. It is goodbye from me now, we canjoin the bbc news teams where you are. This is bbc news. The headlines at 6. 30pm a 27 year old man is arrested in whitehall by armed officers after an Intelligence Led operation. Several knives were discovered at the scene. The Prime Minister who wasnt in Downing Street at the time is being kept informed of developments. I think it shows that our police and Intelligence Security services are on the alert as they always are and are looking to keep us safe and secure. The foreign secretary, Boris Johnson, says britain could take Military Action against the Syrian Regime without a vote in the house of commons. The Labour LeaderJeremy Corbyn has insisted that uk must work through the United Nations to find a political settlement in syria. The government loses a court bid to delay publication of its Air Pollution strategy until after the General Election. New figures show a big rise in Violent Crime in england and wales, with knife crime at its highest level for six years. In a moment it will be time for sportsday but first a look at what else is coming up this evening on bbc news. Well be bring you the latest on that Security Incident on whitehall and well be speaking to a former head of Counter Terrorism at the ministry of defence. Well hear from live theresa may, in the next few minutes, as she makes a speech in leeds as part of the General Election