[TillE]

There are many many thorny issues to be untangled. It's not as simple as saying "we're leaving"; Britain's membership in the EU is a complex thing that's going to take a lot of work to dissolve. The Article 50 negotiations are about those issues, not a future trade deal.

If you just walk away, you leave a mountain of chaos that would have to be handled in courts.

[gaius]

Sure, but it takes two to tango. The EU can't force the UK to wait two years because the UK can simply walk away. This is a loophole that the writers of Art 50 didn't consider.