Poor Sir John Sawers, the next “C” at MI6 (“C” is for Chief, in case you are wondering), whose cover was blown by his wife when she posted pictures of him on her Facebook page. I say “poor Sir John” not because I think that the actions of his missus constitute a huge breach of national security, but because I would not welcome shots of myself in my swim shorts being held up to scrutiny by millions of people.

Worse still, any secret service employee spotted in trunks must inevitably prompt comparison with the most famous image of a British spy in swimmers: 007 emerging from the waves in his blue skimpies in Casino Royale.

When Daniel Craig surfaced in a scene reminiscent of Ursula Andress’s famous appearance in a white bikini in Dr No, he had squeezed his V-shaped, highly honed body into a pair of blue La Perla GrigioPerla swimming trunks. The scene set women’s hearts a-fluttering and men’s teeth a-gnashing and apparently led to a run on the style because of the pre-release publicity shots.

I’m not sure what brand Sir John is wearing on Facebook, but the Foreign Secretary appears to have some inside information. David Miliband brushed off the suggestion that the incident constituted a security risk when he told Andrew Marr Show on BBC One: “It is not a state secret that he wears Speedo swimming trunks; for goodness’ sake let's grow up.”

The Mutton cannot confirm whether they are Speedos or not — a cursory glance at the Speedo website suggests not — but the good news for Sir John is that he is certainly on trend. The model he is sporting is a retro-style trunk with short legs, of the type made famous by Burt Lancaster in the 1968 cult film The Swimmer. This style is widely available and my favourites include the Setter by Orlebar Brown, the Classic Swim Shorts by Paul Smith and Speedo’s range of 14cm swimming trunks.

Let’s face it, if he had been wearing briefs we’d have thought the look a little too “school swimming gala”, and if it had been long board shorts we’d have muttered darkly about him aping a surfer dude attitude. For a man of Sir John’s vintage and standing, his trunks are surely the appropriate choice, Speedo-branded or not.

Much more worrying than the future head of MI6’s choice of swimwear is the revelation from the Conservative MP Patrick Mercer, who is the chair of the counter-terrorism sub-committee, that military chiefs had warned that the Taleban get 80 per cent of their intelligence from Twitter and Facebook.

If that is the case, they must think that they are facing an enemy that routinely gets hammered on cheap cocktails, snogs on sweaty dance floors, suffers from chronic sunburn and has an unhealthy fascination with domestic pets. No wonder they are rattled.