No good turning back. Well, it will take more than two years, more than five years, because look how long that they talk about it. Weve just got to go in and show them that we do mean business. And well be looking at the Prime Ministers hint that cooperation on security is closely linked to the outcome of the brexit deal. Also tonight, a reminder of the Security Threat here in the uk. A crowd converges on westminster bridge, to remember the victims of the Terror Attack which took place here a week ago. Well have more reaction and opinion to todays historic events, as the Prime Minister triggers britains exit from europe. Well hear from politicians, business and members of the public. Thats tonight, here on bbc news. Good evening. The United Kingdom has formally served notice that its leaving the European Union. A letter signed by theresa may was handed to the president of the European Council today. The Prime Minister told mps she wanted a smooth and orderly brexit, but she also hinted