This is almost certainly a collosal act of self-harm, and deeply short-sighted. I was desperately hopeful that the whole Brexit situation could be salvaged in some way, and that some way forward for liberalism might be figured out such that the rising tide of populism could be countered. I'm less and less confident about that.
Parliament has to vote on it... might be hope
When Parliament gets its vote, the two year exit period will almost certainly be almost over and a vote of Parliament will not be able to stop the exit. Instead it will be a vote on the new arrangements with the EU. So either they just have to rubberstamp whatever gets put to them or - if they vote down these new arrangements - Britain will be left outside of the EU without any new deal in place.