Its a day that marks the biggest change in britains relationship with its european neighbours in nearly half a century. Im pleased that brexits happening cos i think itll be good for our country to get back to have our own rules and regulations. Well have control of our borders again. The governments embarking on a journey and it has no idea where its going, it doesnt know what its doing and anyhow its not in control of negotiations from now on. Well be reporting from westminster and beyond on the day people also remembered the Terror Attack which took place a week ago. Many people converged on Westminster Bridge to remember those who lost their lives and those injured when the attack took place last wednesday afternoon. Its 5 oclock. Were live at westminster on the day the United Kingdom formally serviced notice that it will leave the European Union. It signifies the biggest change in britains relationship with its european neighbours for nearly half a century. A letter signed by theresa may was handed to the president of the European Council donald tusk at lunchtime. The letter activates article 50 of the Treaty Of Lisbon marking the formal start of two years of negotiation. The Prime Minister told mps she wanted a smooth and orderly brexit with as little disruption as possible which would see britain become fairer and stronger. The chief eu negotiator Michel Barnier said that today was the first day in a very long and difficult road. Lets look at some of the key points of theresa mays historic letter. She said we want to remain committed partners and allies to our friends across the continent. She talks of a new deep and special partnership with a strong European Union, taking in both economic and Security Cooperation. The emphasis on security has been underlined some viewing it as a potential threat to the eu. She says people and businesses in the uk would benefit from implementation periods to adjust in a smooth and orderly way. And she says the task before us is momentous but it should not be beyond us. Well be discussing the letter and what it says about the uks likely Negotiating Strategy and well have reaction here at westminster and beyond. We start with our Political Correspondent carole walker. This was the moment the uk really began its departure from the European Union. The British Ambassador to the eu, sir tim barrow, handed the president of the European Council, donald tusk, the letter signed by the Prime Minister. It was the formal notification triggering the start of brexit negotiations. Minutes later, the Prime Minister confirmed the significance of the moment. The article 50 process is now underway and in accordance with the wishes of the british people, the United Kingdom is leaving the European Union. This is an historic moment, from which there can be no turning back. Britain is leaving the European Union. We are going to make our own decisions and our own laws. We are going to take control of the things that matter most to us. She spoke of her fierce determination to get a deal that works for everyone, but acknowledged the consequences of brexit. We know that we will lose influence over the rules that affect the european economy. We know that uk companies that trade with the eu will have to align with rules agreed by institutions of which we are no longer a part, just as we do in other overseas markets, and we accept that. However, we approach these talks constructively, respectfully, and in a spirit of sincere cooperation. In her letter, theresa may says she wants a deep and special partnership with the eu outside the Single Market, but with a bold and ambitious free trade agreement. She wants to continue co operation on security, a deal on transition periods to avoid a cliff edge for businesses and investors and she wants an early agreement on the rights of eu citizens in the uk and british citizens in eu states. Already its clearjust how hard it is going to be for the Prime Minister to fulfil her ambition of bringing the country together. There are stark divisions in her party, in parliament, and across the country. People have very different views on what they want and expect from a brexit deal. The snp dismissed the Prime Ministers talk of unity. On this issue, it is not a United Kingdom and the Prime Minister needs to respect, respect, the differences across the nations of the United Kingdom. If she does not, if she remains intransigent, and if she denies scotland a choice on our future, she will make Scottish Independence inevitable. The vote, having been taken, the decision having been given to people of the United Kingdom, that we should now respect that vote and get on with the job of delivering for everybody across the whole of the United Kingdom. The Labour Leader warned her not to listen to hard line tory ideologs. The direction the Prime Minister is threatening to take this country in is both reckless and damaging and labour will not give this government a free hand to use brexit to attack rights, protections and cut services or create a tax dodgers paradise. And some conservatives urged her not to walk away without a deal. Does she not agree with me it is time to Start Talking facts and sense to the british people rather than rhetoric and ideology and in particular, rejecting the idea that no deal and a reliance on wto rules would somehow be ok . Theresa may said she would work hard to reach a comprehensive trade deal. Her predecessor said she was doing an excellentjob. Her predecessor said she was doing an excellent job. We were in the eu and now i hope we may be out of the eu but in it in terms of cooperating over security and common interests and reaching a good deal. So, we have the Prime Ministers objectives in writing. Now, the work begins to get an agreement which is acceptable across the eu, and across the uk. In brussels as we heard donald tusk the president of the European Council conveyed a Farewell Message to the uk saying we already miss you, thank you and goodbye. . He said this was not a happy day for the European Union orfor britain, in his view. He confirmed he would set out his Draft Negotiating Guidelines on friday ahead of an extraordinary summit of the remaining 27 Member States. Then the serious talking can begin as our correspondent Richard Galpin reports. The uk Permanent Representative to the European Union said Tim Barrow Setting off this morning on a mission that will make history. He is personally delivering a letter from theresa may formally notifying the eu that the uk incense leaving after 44 years as a member. For the man who received the letter, the president of the European Council donald tusk, this was a moment of profound disappointment. There is no reason to pretend that this is a happy day, neither in brussels nor in london. After almost after all, most europeans including almost half the british voters wished that we would Stay Together and not drift apart. Our goal is clear. To minimise the cost for the eu citizens, businesses and Member States. It was back in 1973 that the ukjoined what states. It was back in 1973 that the uk joined what was then called the European Economic community. The Prime Minister at the time ted heath pledging to expand it further. The european communities far from creating barriers, have served to extend east west trade, britain i hope you will agree, has much to contribute to this process and as members of the community we shall be better able to do so. But over the following decades the relationship became increasingly rocky. As the eu move towards much greater integration. Last weekend with the uk already clearly on its way out, the remaining 27 Member States met in rome to pledge their allegiance to the eu. A sign of unity in the crisis sparked by brexit. And this afternoon the eu prozac most powerful leader made clear that brexit negotiations will not be as theresa may had wanted. A divorce and any future relationship with the eu will not be discussed in parallel. We know there are type commitments between the uk and the eu in the negotiations it must first be clarified how we go about dismantling these commitments. And also about how we deal with the many rights and duties tied up with membership up until now. It is only if we have sorted that out that we can next and i hope soon, Talk About Oui can next and i hope soon, talk about our future relationship. And that could lead to an early row between brussels and london. Even more serious could be the eu demand that the uk should pay around £50 billion as part of its divorce settlement. Well in a moment we would be speaking with former conservative cabinet ministerJohn Whittingdale. 0ur chief Political Correspondent vicki young is in the central lobby of the houses of parliament. That letter from theresa may, that letterfrom theresa may, can you take us through it and what stood out for you. Well there were no huge surprises but it does show the huge task that the uk has ahead of it. With theresa may breaking down into various areas what needs to be decided as the uk extract itself after as we heard, more than 40 itself after as we heard, more than a0 yea rs of itself after as we heard, more than a0 years of this incredibly close economic cooperation. And picking up on what we just heard about there, the whole idea of what is decided during the talks. Actually they will have to have talks about what is in the talks before even starting and there is a big dispute right at the beginning of this. In the letter she says we believe it is necessary to agree the terms of our future partnership alongside those of our withdrawal from the eu. Partnership alongside those of our withdrawalfrom the eu. That partnership alongside those of our withdrawal from the eu. That is what the eu have just withdrawal from the eu. That is what the eu havejust said withdrawal from the eu. That is what the eu have just said they will not agree to. So she feels strongly, you cannot just agree to. So she feels strongly, you cannotjust decide how much money the uk owes the eu, if any, you cannot just the uk owes the eu, if any, you cannotjust decide what happens to eu citizens, you have to think also not just about the divorce but think about the future relationship and do that in parallel. Already that seems to bea that in parallel. Already that seems to be a big moment of contention. Then if you turn to the idea of no deal at all, much has been said about this, theresa may saying before that no deal was better than a bad deal. Interestingly she did not repeat that today, she says that would not be the ideal situation having no deal but then goes on to say in security terms, a failure to Reach Agreement would mean our cooperation in the fight against crime and terrorism would be weakened. She says the uk and the eu would of course cope with no deal but she says it is not what theyre working towards, think clearly they do want this. Interestingly the reaction from the eu has been quite negative, saying linking the idea of a trade deal with security is a threat. Downing street totally deny that and say it is not about that, that and say it is not about that, that we will stay in nato and still cooperate, but that Cooperation On Security will not be as close. So theyre using the web threat in this particular circumstance and yet we have heard others described the letter as being constructive in its tone. How do we square those things . I think the rest of it is, if you look at it, the language she uses, talking about a shared interests we have had with the eu and will continue to have. And several times, five times i think she talks about a deep and special partnership. The point theyre making and the point the government will make is that the uk is not like any other third country that the eu might deal with. Because we have been so closely involved for more than a0 years, so weve had the same approach, we have the same regulations, we have had this entwining of so many aspects of oui this entwining of so many aspects of our life. But that would make it in fa ct our life. But that would make it in fact easier to have this very close relationship as we go on whether it is some kind of bespoke deal with details of course which will need to be thrashed out. And finally for the moment, so much focus in the Referendum Campaign last year and the talk afterwards about Freedom Of Movement and levels of migration and immigration, what did the letter tell us about that aspect. Specifically it was not mentioned, it was mentioned in terms of the fa ct it was mentioned in terms of the fact that theresa may has laid out before that the uk is going to leave the Single Market. The reason for thatis the Single Market. The reason for that is because you cannot stay in the Single Market and not accept Freedom Of Movement. And she believes very much, her interpretation of that Referendum Result is that people voted to end Freedom Of Movement because of levels of immigration. Of course the interesting thing about this, just a couple of days ago the brexit secretary david davis when asked about that had a different emphasis and said it is all about controlling the borders. And actually made the point that we may need immigration, we will meet immigration still in the workforce and it could go up or die, but the principle for him and others is that we can control it. I think the point of all this is if this is going to have to be a compromise, a compromise with the eu and also a compromise for some of the people sitting on the backbenches who many would think we Canjust Go Backbenches who many would think we can just go out without a deal and will be perfectly 0k. Can just go out without a deal and will be perfectly ok. But the problem with the compromise of course is you end up in a situation where no one is happy. Thank you very much. Joining me isJohn Whittingdale the former conservative cabinet minister and someone who advocated britains exit from the eu. What does today signify. It is the beginning of what will be a long process but also a day on which the government has carried out the wishes of the british people and is expressed in the referendum last june. Expressed in the referendum last june. The tone of the letter today, seen here by many as constructive andindeed seen here by many as constructive and indeed the contrast with some of the statements from the Prime Minister in the past six months, others in brussels see it in a different way. How did you read it. Of course it is constructive because we wa nt of course it is constructive because we want to have as amicable departure as possible. It is important that we try to reach an agreement allowing our businesses still to trade in europe, allowing us still to trade in europe, allowing us still to cooperate on things like security policy, foreign policy. And it is in everyones interest that that be achieved. People in europe will suffer, companies in europe will suffer, companies in europe will suffer, companies in europe will suffer as much as British Business if we cannot Reach Agreement. The Prime Minister made that clear. And also stated we hope we can remain very close partners with the other countries in europe but outside the eu. Are some leaders in brussels correct to think this endless coupling of security with trade for example, within the context of a broader agreement, is akin toa context of a broader agreement, is akin to a threat. I do not think it isa akin to a threat. I do not think it is a threat at all, both are important. Cooperation in Security Matters is incredibly important, we have seen the reasons why in the last few weeks. And that must be a priority. But there are many other issues and achieving open access to markets in europe and allowing european firms to trade in the uk as well is also in our economic interest. These are all Big Questions which we now have to sit down and resolve. Reading between the