It is an irony Boris Johnson might appreciate that the debate over Scottish independence has become a mirror image of the pre-2016 arguments over Brexit. The prime minister and his Conservatives say Scots are better off “remaining” in a strong union with their largest trading partner. Independence supporters appeal to national pride and identity — to taking back control, to coin a phrase. And their argument is gaining ground. Mr Johnson’s misfiring visit to Scotland last week will do little to reverse polls that for the first time show more Scots favour ending the union with England than keeping it.

This is disturbing, if not unexpected. Scots voted 62-38 in 2016 to remain in the EU. Having Brexit imposed on them has prompted a chunk of the 55 per cent who voted to keep Scotland in the UK in 2014 to switch sides. Covid-19 has compounded matters. Neither the death rates — Scotland’s is only slightly below England’s — nor policies have been wildly different. But the clear communication of Nicola Sturgeon, the first minister and Scottish National Party leader, has turbocharged her approval ratings compared with the bumbling Mr Johnson.

Ms Sturgeon has been helped by the failure of ineffectual Conservative and Labour leaders in Scotland to hold the SNP to account over its poor domestic record in, say, health and education. It is another irony that Mr Johnson’s desire to preserve the union would benefit from the resurgence of Labour in Scotland as another credible alternative to the SNP.