Boris Johnson won the general election of 2019 on the promise that he would get Brexit done. But it has not been done. Instead of stabilising, post-divorce relations are worsening. Not surprisingly, they are most fraught where the responsibilities remain shared. Fisheries are one such point of contention. But the most dangerous by far is Northern Ireland. Back in October 2019, Johnson declared he had reached a “great new deal”. Now he would like to tear it up. That is characteristic, alas. But it is dangerous not just for the UK, but also for the EU and wider west.

In one sense, Brexit could never have been “done” by now. The ending of a marriage transforms the prospects of the partners into the future. Other things equal, the more economically dependent partner will also suffer more.

In its Economic and Fiscal Outlook last month, the Office for Budget Responsibility concluded that “since?.?.?.?November 2016, our forecasts have assumed that total UK imports and exports will eventually both be 15 per cent lower than had we stayed in the EU. This reduction in trade intensity drives the 4 per cent reduction in long-run potential productivity we assume will eventually result from our departure from the EU.” To put this in context, this is twice the estimated long-run costs of Covid and, in today’s value, is ￡80bn a year.