However much time and money is poured into the research, there seems no prospect of an effective vaccine for Boris Johnson’s recurring foot-in-mouth disease. His latest departure from his party’s approved script came in a Zoom call to his northern MPs, when he delivered some impromptu thoughts on devolution to the nations and regions. Devolution in Scotland, he said, had been a “disaster”, probably “Tony Blair’s biggest mistake”. (A somewhat startling observation in light of a certain invasion.) So Johnson is very definitely not in favour of ceding any further powers to the devolved administrations. These remarks, not unexpectedly, were manna from heaven for those Scottish nationalists agitating for a second independence referendum to follow the Scottish parliament election next May. Fourteen consecutive polls have put support for independence in the lead, while the Scottish National party appears on course to have a sizeable majority in the new Holyrood parliament. Against that backdrop, you might imagine that the prime minister would be exceptionally careful in his choice of words. Let’s not forget that on his elevation to No 10 he pronounced himself prime minister and “minister for the union”. A new post, presumably to underscore just how precious the ties that bind Britain’s nations are. This latest gaffe may have profound consequences at a time when Covid-19 has laid bare the tense relationships between Westminster and the devolved parliaments in Cardiff, Belfast and Edinburgh. Above all, Johnson’s remarks will have intensified the fury already sparked by the internal market bill. Understandably, most of the commentary on this bill has centred on the government breaking international law by reneging on the withdrawal agreement with the EU. Yet the debate in Scotland centres on the bill’s repatriation of powers from Brussels to London, including powers previously held by the devolved governments. Widely perceived as a Westminster “power grab”, this proposed diminishing of devolution has proved a powerful accelerant in the push for independence. Ministers have claimed it is nothing for the Scots to worry their little heads about – merely a tidying-up exercise to make sure that chicken, chlorinated or otherwise, will have the same standards throughout the UK. Yet given that Johnson is commonly regarded north of Hadrian’s Wall as the SNP’s most effective recruiting sergeant, his latest musings will only reinforce that thinking. If he really believes no further powers should ever be embedded in devolved governments, it also blows a hole in the strategies of all other parties who oppose Scottish independence. Gordon Brown, following the 2014 referendum, assured his Scottish Labour troops that there would be the most potent ever form of federalism within two years. On the Andrew Marr Show last Sunday he suggested that now was not the time for any constitutional rearrangement. In early 2015, Labour had 40 Scottish seats in the Commons; now it’s just one. The polls suggest that the party’s continuing hostility to independence and, most recently, to another referendum, has caused mass migration to the SNP. And Johnson’s latest thoughts suggest any notion of stronger federal powers is fanciful. But if you have sympathy to spare, save it for the Scottish Conservatives. Under Ruth Davidson, and against the UK trend, they won 13 seats in 2017. In the last election they lost seven of them. Davidson has now accepted a peerage from the prime minister she once apparently despised. Her initial successor has come and gone. The latest Scottish Tory leader is part-time football referee Douglas Ross, the MP for Moray. How he must long to give the boss a red card. • Ruth Wishart is a Scottish freelance columnist and broadcaster