hould we all be wearing masks to go out in public? Sadiq Khan, London’s Mayor, publicly broke ranks last week to argue for compulsory face-covering on public transport and as I write, the government’s scientific advisers are re-reviewing the pros and cons after Germany and the US started recommending masks for ordinary members of the public. Fears remain that a run on masks could either leave NHS workers dangerously short of them or make wearers overconfident, if they don’t realise that mask-wearing is about trying to protect other people rather than yourself. But look around your nearest supermarket to see how many people are no longer waiting for ministers to make their minds up; at the weekend, I spotted everything from strategically positioned scarves to cycling kit, builders’ dust masks and home-stitched floral numbers. Whatever the experts conclude, Khan seems to be going with the grain of public instinct, and if the advice does ultimately change then he’ll have left government looking slow-footed even if it has hesitated for the best of reasons. (Ministers are taking their lead from the World Health Organization, which still isn’t recommending masks for general public use.) But this isn’t just about masks. The inevitable leadership vacuum created by Boris Johnson’s illness is starting to be filled less by ambitious lieutenants – although the news of an anonymous Downing Street source briefing against Matt Hancock’s promise of 100,000 tests a day suggests things are getting alarmingly fractious – than by emboldened devolved leaders. Nicola Sturgeon has already warned Scotland won’t necessarily follow whatever path Johnson eventually sets out of lockdown, promising to treat Scots like “the grownups you are” by laying out her own personal thinking this week. (The echo of Angela Merkel, praised for providing detailed explanations of the science underpinning her decisions rather than fobbing off tough questions with invocations of Dunkirk spirit, is surely deliberate.) Even Wales’s first minister Mark Drakeford, while worrying that it would be harder to enforce lockdown rules that varied across the country, has said he would “do things differently” in Wales if necessary. If Downing Street tries to lift the lockdown too quickly, it could trigger a constitutional showdown like that unfolding in the US, where individual state governors have chosen to protect their citizens by defying Donald Trump’s attempts to reopen the economy. And while it’s one thing brushing off questions about why Britain isn’t doing what South Korea is doing, it’s quite another explaining why Scotland appears to have no confidence in your strategy. A cynic might say all this is dangerous game-playing by Labour and SNP politicians facing elections next spring, who won’t want to be seen as having blindly followed in Westminster’s footsteps if by then the public mood has turned. (For now, polling shows voters are still more supportive of this government’s handling of the epidemic than the left likes to think, although with doubts creeping in about NHS workers being properly protected from the virus; the failure of a much-vaunted big shipment of protective equipment from Turkey to materialise forms part of a bigger worrying pattern of overpromising and underdelivering.) It does the Scottish nationalist cause in particular no harm for Sturgeon to emerge looking like a plausible alternative to Westminster leadership in a crisis. But you can’t devolve education and health policy and then expect devolved governments not to use their powers in a once-in-a-generation emergency, and nor can practical differences to everyday lives be ignored. Talking about schools possibly starting to come back in July, fitting in a few weeks’ teaching before the holidays, makes sense in England but not in Scotland where schools break up at the end of June. Masks could well give city-dwellers confidence about getting back on the Tube, but would the balance of risks and benefits be the same in sparsely populated rural areas where most people drive to work? Half the point of devolution was to acknowledge that what works for one part of the union doesn’t always work everywhere, and to manage the resulting tensions. But when the centre starts to falter, looking uncertain or divided, it’s in the nature of politics that rival power bases will grow. If Downing Street doesn’t get a grip, the next public spat may be about something more fundamental than a piece of cloth. Gaby Hinsliff is a Guardian columnist.