Just in case anyone is unclear about the process for withdrawing from the European Union, the British Government has produced a guide (
link).
I don't think many people understand how difficult it will be for Britain to get any kind of good deal. Once article 50 is triggered, the terms of negotiation have been agreed by the European Council and the European Parliament. Both bodies have to vote on the EU Commission's proposals. Anyone who saw the reactions of people like Juncker and Schultz to the Brexit vote must understand how hard it will be. Even if the members of the European Council e.g. Merkel, wanted a good deal for Britain, she would have to get it past a majority of the European Council and the European Parliament. The latter body is especially Eurofederalist and will be looking to punish Britain for damaging the so-called European Project.
David Cameron actually got a pretty good deal from his renegotiation, a deal those bodies had agreed to implement if we voted to remain. Now we have left...
Anyone who saw the foreign ministers on TV today will note there is little willingness to show Britain any patience.