My instant response was to recoil. The recoil makes the point (on reflection) more eloquently than words and analysis alone can do. I doubted I should venture onto this tricky ground. Too many of my own friendships, personal and professional, are involved.

“I know David Blunkett a little,” I thought. “He wrote me a nice letter wishing me well when I quit The Times’s parliamentary sketch; and I wrote back wishing him well in Cabinet, and got a friend to write the letter for me in Braille.

“And then too,” (I thought), “I’m on the friendliest of terms with Boris Johnson, both as the Editor of the magazine for which I write, and as a Tory MP — as I used to be. His former lover, Petronella Wyatt, and I hold each other in mutual affection. At least I hope so: I’ve always liked her. She once wrote a column in which she asked, no doubt teasingly, why I would not sleep with her.

“As for Kimberly, we’ve always got on like a house on fire. I love her mischievousness and find her completely beguiling; no one can make me laugh as Kimberly does. We had a marvellous lunch together at The Ivy before she remarried — and only a few weeks ago (it seems) I was sitting beside her and her new husband, Stephen Quinn, at the Spectator Parliamentarian of the Year Awards dinner at Claridges: a monster gathering of MPs and journalists where Michael Howard made that cheeky speech about Boris Johnson. Kimberly had us all in stitches with her account of her attempt to use a vacuum cleaner (“I called my mother in America. She said ‘check if the bag’s full’. I checked. ‘No, no problem, mother, I said: it’s completely full’. I thought it was like a car’s gas tank. I didn’t realise it had to be empty.”)

“And of all these people,” I mused, “I think I count Simon Hoggart as the best of friends. A nicer, more generous and less devious man you couldn’t hope to know. As soon as I heard the news about him and Kimberly I sent him a text message reminding him how soon all this would pass, and he could return to the job at which he’s the best living practitioner in British journalism: the job of cheering us all up.

Only last summer I called in on Simon and his wife and family holidaying in France, then drove on to visit Lance Price (Alastair Campbell’s former deputy at No 10) at whose holiday house I discovered Tony Wright, the excellent Labour MP, in the swimming pool with his wife. Tony’s wife, that is, thank God.”

“Oh – and then there was that paeon of praise I heaped on the absent Boris at a Tory luncheon in Wantage, a constituency close to Boris’s, where I spoke last month in the cause of their prospective Conservative parliamentary candidate, Ed Vaisey. Ed (who works for Michael Howard) persuaded me to do this when we met at a wedding in Moscow in October. The groom at the wedding was Ben Wegg-Prosser, formerly Peter Mandelson’s assistant, who is now at The Guardian . Peter turned up at the wedding, in stylish brown corduroy. The best man was Tristram Hunt. Half The Guardian were there, and so was Anji Hunter, formerly Tony Blair’s gatekeeper, now head of communications at BP — oh, and Anji was with her partner, Sky News’s anchorman, Adam Boulton. In Moscow I made the acquaintance of the excellent Rachel Whetstone, who helps Ed look after Michael Howard, and . . .”

But I think I’ve made the point. Two worlds so close, so interlocking, so shaded — one into the other — that I sometimes think they are not two worlds, but one, and we’re all on the same side. So it isn’t really sleeping with the enemy at all.

But it has to be asked: should heterosexuals be permitted to occupy important or sensitive posts in our country? I’m as tolerant of diversity as the next man and would never condone the persecution of anyone solely on account of his or her sexuality, so this is not a moral judgment but a practical one.

Simple observation suggests — and the last couple of months of newspaper headlines demonstrate — that heterosexuals in public life do seem to find difficulty in maintaining lasting relationships with a single partner. This is a matter for sympathy rather than censure, but can instability at the very core of their lives, in their relationships, be without effect on the stability of their professional judgments?

It may be something about the heterosexual culture rather than inherent in their condition, but promiscuity among them appears to be the norm. This being so, there is obviously a danger of blackmail. For their own sakes as well as the sake of national security and the integrity of our institutions, this is a risk we should surely not want them to run.

Nor can it be conducive to the calm exercise of judgment at work if these people have to lead (as they so often do) a double life: constant anxiety is a potentially destabilising state of mind, and one must ask whether heterosexuals are able to place honesty at the centre of their professional lives when deception rules in the private sphere. Prominent people in the media, as well as senior politicians, are especially vulnerable because they face disgrace and ruin if exposed.

I would not go so far as to suggest that no heterosexual should ever serve in the higher reaches of government, politics or the media. There are a handful of examples of heterosexuals who have made a huge contribution to human history – Henry VIII or the Duke of Wellington, for example, although in both cases their private passions did sometimes get in the way. And even in the Armed Forces there have always been heterosexuals who have shown as much valour and patriotism as their brother officers. I count many heterosexuals among my friends.

But exceptions should not make the rule. On the whole, and until society changes its attitude to the colourful tastes and exotic practices of so many of today’s heterosexuals, then, adore them though we do, it might be better if they were restricted to careers in the arts, hairdressing and airline cabin crew, where their “butterfly” lifestyle is less likely to interfere with the exercise of their duties.

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