LAST week Prime Minister Theresa May signalled Holyrood can expect no real new powers after Brexit.

Yesterday one of her ministers looked like defying that threat. Alas, only briefly.

David Davis, the Brexit secretary, for a few short hours appeared to hint Scotland and other UK nations and regions would get powers to set their own controls on immigration.

Policy, Mr Davis said, must serve the “needs of every part of the UK”. What he did not say – but what was quickly clarified by his superiors in Downing Street – was that the needs of Scotland would be judged in London, not Edinburgh.

This is potentially catastrophic. It is far from obvious Conservatives pandering to anti-foreigner sentiment in England and Wales will set the right course on immigration for Scotland.

This newspaper has long supported the Scottish Government’s legitimate and practical aspiration to tweak UK immigration policies to make sure our businesses and public services have the workers they desperately need.

So too, last month, did a cross-party committee at Holyrood – albeit not its Conservative members. Why? Because MSPs knew just how much fiscal and wider economic peril Scotland is in without new and younger workers.

The arguments are well-rehearsed. Scotland has a lower life expectancy than many other comparable countries, we have lower fertility rates and the population is growing at a slower rate than the UK as a whole. Births fell to a 10-year low, according to figures released on this week.

We may not live as long as the English or other Europeans. But many of us still have long periods of ill health at the end of our lives. We need youth to balance this out. And we are not creating enough young people ourselves. So we have to import them.

Most Scots appreciate this reality. Opinion polls suggest we have more positive attitudes to migrants than our counterparts in England and Wales. That does not mean there are no concerns about immigration in Scotland, legitimate or not.

However, the UK Government must not go on ignoring Scotland’s very different vote on Brexit – and very different stance on foreign workers. Nor should Mrs May’s administration pretend there are insurmountable practical hurdles to a separate or partially-devolved immigration system.

We have, after all, had one before: Jack McConnell’s modest regime for allowing foreign students to stay in Scotland after they graduated.

Indeed, some large states – such as Canada – have differing immigration policies for differing constituent parts. Federal Canada may not be a model the Conservatives now want to follow. Mrs May, after all, has moved away from the “family of nations” rhetoric of her predecessor David Cameron. Instead, she is sounding more centralist.

Last week the prime minister said her ministers would no longer “devolve and forget”. She said she does not want a “looser and weaker” UK. The Union, however, is not strengthened by adopting crude one-size-fits-all policies on issues like immigration. It’s weakened. Mrs May should think on that.