“In principle, at least. In practice I expect that (a) Parliament will make the call,…”
But what will be the options for them when they make their “call”? Bearing in mind that MPs voted by over five to one to invoke Article 50 (and thus trigger our leaving) what will be the consequences if they refuse to sanction the leaving deal? Personally I believe that they should only have the choice of either accepting the deal or leaving without one. The alternative would be endless negotiations which would probably see the UK remain in purgatory whilst endless prevarications take place. If MPs have the interests of the UK at heart (a big if) they should understand that businesses (and indeed everybody else) needs certainty. The certainty of leaving without a deal is far better than the uncertainty of those endless prevarications.