UK’s Withdrawal from the EU

I wish to pursue the question asked by the right hon. Member for North Shropshire (Mr Paterson). Would I be correct in understanding that these discussions that are going on about the backstop relate purely to the next phase of the negotiations and what can be done in relation to the political declaration, and do not involve any question of opening up the withdrawal agreement and changing its force? That is right, is it not? If we look at the Prime Minister’s statement yesterday, we see that it was all about the next phase—a “work stream in the next phase”, as the right hon. Gentleman just said. Will he clarify that: it is not about opening up the withdrawal agreement?