Article 50
It hasn't been triggered yet. (and it might never be)
Once triggered Article 50 is irrevocable (ECJ will agree).
If and when it is triggered there is a two year negotiation period on the terms of exit.
There will be no negotiations on future treaties until after exit (this has been made clear).
With agreement of all other EU members, the negotiations can be extended (for an unspecified period).
In agreement with all other EU members, exit can be triggered at any time before the two year period expires.
The UK and the rest of the EU could however make staying in the EU an agreeable negotiating position on the terms of exit, there is nothing in the treaty precluding this outcome (the Hotel California option).
All this talk of trade treaties is irrelevant, there can be no negotiating of any new treaties between the UK and the EU until after Exit has occurred.
Biting the hand that feeds IT
