It is a fundamental mistake for the Chancellor to underestimate the impact of Brexit on his future forecasts. To dismiss the 3.2% collapse in the forecast for business investment is a strategic error that he is making for the future. We hear the Chancellor talk about a “deal dividend” and the shadow Chancellor talk about a “jobs-first Brexit”, but that is a mythology. Brexit in all forms will hit our business investment and our tax revenues and create austerity for a decade. Can the Chancellor and the shadow Chancellor stop treating this as business as usual?