It is a thoroughly good thing when ex-Prime Ministers stay in the Commons, as Theresa May has, to give their fellow MPs the benefit of their views, knowledge and experience – that last being, as Oscar Wilde once put it, “the name we give our mistakes”.

Parliament is the poorer for not having John Major, Tony Blair, Gordon Brown and David Cameron in place – perhaps because they are unwilling, understandably enough, to declare their interests, and then see them prodded and poked by a not always kindly media.

At any rate, Theresa May should be praised for following in the footsteps of Edward Heath, who stayed an MP after leaving Downing Street in 1974, remaining in the Commons for the best part of 25 years.  Though in the course of that time he was sometimes described as “the incredible sulk”, a fate she will doubtless avoid.

On which point, her intervention in the Commons yesterday, about David Frost’s appointment as National Security Adviser, was explosive but not necessarily right.  Let me begin explaining why by thanking Dean Godson, the Director of Policy Exchange, for reminding me of part of my own story.

During the run-up to the 2010 general election, I served on Cameron’s front bench as part of the pantomine horse tasked with integration and security policy.  Eric Pickles led the integration end, assisted by Sayeeda Warsi in the Lords and me in a more junior role in the Commons.

The security end was led by David Davis.  Which was the front end of the horse and which the back you must judge for yourself, but he was supported by no less a person than the redoubtable Pauline Neville-Jones, who had been appointed as David Cameron’s National Security Adviser.

Neville Jones had been a civil servant, but was one no longer – obviously, or she wouldn’t have been able to serve an Opposition Party.  In other words, she was, like Frost, a political appointment.  And she was set to take up the post in government on the same basis.

That didn’t happen for a variety of reasons – but they had little if anything to do with her no longer being a civil servant.  This slice of history is a reminder that the American-style title of National Security Adviser is relatively new.  And in the United States, of course, political appointments are the rule rather than the exception.

There’s no reason why it should necessarily be different here.  The wall between political and diplomact appointments is sometimes vaulted – as when Jim Callaghan sent Peter Jay to Washington as Ambassador or, more recently, when David Cameron’s former Chief of Staff, Ed Llewellyn, was dispatched in the same capacity to Paris.

I don’t remember Llewellyn’s appointment creating waves.  Then again, he was a Remainer before and during the EU referendum whereas Frost was not.  Could this explain why some of the protests about the latter’s appointment are made so passionately?

May would say not – claiming yesterday that Frost has “no proven expertise in national security”.  And, certainly, he has less experience in the field than Mark Sedwill, the ex-Prime Minister’s former Permanent Secretary at the Home Office, who eventually followed her to Downing Street, and to whom she is clearly committed.

Sedwill was Ambassador in Afghanistan, then NATO’s Senior Civilian Representative there, then the Foreign Office’s Director-General for Afghanistan and Pakistan and also its the Director-General, Political.  But hang on a moment.  Sedwill has three predecessors as National Security Adviser.  What about them?

Peter Ricketts, the first holder of the post, was the Permanent Representative to NATO and Chairman of the Joint Intelligence Committee.  Fair enough.  But Kim Darroch, the second, was essentially an EU specialist – eventually serving as Permanent Representative, i.e Ambassador, to the European Union.

Mark Lyall Grant, the third, was the Foreign Office’s Director General for Political Affairs before becoming Ambassador to the United Nations.  That former post will have left him familiar with the world of spookdom.  But so will Frost’s experience as Director of the Foreign Office’s Policy Planning Staff.

He will also have had to be across security issues as Boris Johnson’s leading policy SpAd when the latter was Foreign Secretary.  Did Darroch really have more “proven security expertise” on appointment as National Security Adviser than Frost?

Britain is not the only country to be restructuring its national security system in response to what is proving not to be “the end of history” but the revival of ideology – be it communist in China or Islamist elsewhere (including, in case anyone had forgotten, here).  Then there is Russia.

Godson says that “as part of Global Britain – foreshadowed by his speech on the EU earlier this year – Frost is going to be much the most high profile holder of the National Security Adviser post. He is going to be a super Ambassador, a direct emissary for the Prime Minister”.

But perhaps we should all take a step backwards from comparing CVs, and simply ask ourselves who has a record of delivering for Britain.  With all due respect to the former Prime Minister, her version of the Withdrawal Agreement, negotiated with Olly Robbins in the lead, failed to pass the Commons three times.

The variant negotiated with Frost in place actually won MPs’ support before last December’s election.  The EU Withdrawal Bill of which it was the centrepiece gained Second Reading, though the Government lost the timetable motion which came with it.

And of course Brexit itself, with the Johnson/Frost Withdrawal Agreement in place, has now happened.  Is it really so bad to appoint a National Security who actually believes in it – and who has the full confidence of a Prime Minister elected by a thumping majority only last December?