Ruth Davidson won the leadership of the Scottish Conservatives on the principle that it would be better to make a virtue of their being part of a wider British party than sever that connection and break away.

She beat Murdo Fraser to the crown in 2011, but the idea that the toxicity of the Tory brand north of the border was terminal didn’t go away – especially after a record low result in 2015.

But this week’s Budget speech marked the latest step in what is proving a very thorough vindication of Davidson’s loyalty. If the June election showed that the Conservatives can win Scottish MPs, the Budget illustrated how useful they are.

There’s obviously the raw parliamentary arithmetic: given the closeness of the result there is no doubt that the 12 gains in Scotland were crucial to keeping Theresa May in office. But there’s much more to it than that.

An effective Scottish caucus serves as a conduit between the Government and Scottish opinion, representing and defending national policy to their voters whilst providing on-the-ground intelligence and a lobby for Scottish concerns inside the Party.

When the Tories were wiped out in Scotland in 1997 this vital link was cut, making it increasingly hard to reverse as the Conservatives evolved – as all parties continually do – with inadequate Scottish input. (The loss of so many urban seats likely had a similar effect in cities.)

That feedback mechanism has been restored, and the Budget speech showed it: not only were there more Scotland-friendly policies than might otherwise have been the case, but they have secured expansive coverage in the Scottish press too.

Armed with the Budget, the Tories are now arguing that their 13 MPs have delivered more for Scottish voters than the SNP’s huge caucus has ever managed. What makes this such a particular triumph for Davidson is that this argument hinges on making a virtue of precisely what she based her leadership pitch on: membership of the national Conservative Party.

That Scotland’s interests are best served through friendly and effective cooperation in British politics and institutions must be the very essence of the unionist case. In 2011 this crucial argument was almost abandoned, but Wednesday’s events showed that the Conservatives can now press it in earnest.