This is complete codswallop in any case. Unless we could somehow have two Britains, one having undergone Brexit and the other not, side by side for comparison for the next 50 years, we will never know what the long-term impact of Brexit was. Things change in the world at a rapid pace. Nothing is predictable these days. No one is going to be sitting around in 50 years' time saying "There you are! That's what brexit did for us!" Jake Greasy-Mug is having us on. By giving brexit a bye for the next fifty years he's exonerating himself in advance for when things go badly wrong in the next three or four years. When the pound has collapsed and we've made made no progress making deals and we find that we still have to deal with the EU, only on far more disadvantageous terms, he can say "Don't blame me! We haven't given it long enough! My reputation remains inviolable until I'm pushing up daisies!"