Hell, observed that relentlessly jolly fellow Jean-Paul Sartre, is “other people”. Obviously, he never had to endure triple French, grinding through that unputdownable masterpiece of his, Les Mains Sales – for which I sincerely hope he is discovering a whole new circle of damnation, and without anyone around to distract him from it. People, he might discover, have their uses. Even in hell.

In any case, judging by the increasing popularity of “single-unit living”, an awful lot of people must agree with him. I don’t – though there’s no doubt that people can be annoying, especially at breakfast, as discussed previously. And, of course, I wish they didn’t spill paint on the carpet or infect me with their wretched classroom nits. In an ideal world, I suppose, they would all sit stock still in another room, watching television with the volume off.

Nevertheless, and in spite of the unquestionable hellishness of people everywhere, let alone within the living unit, heaven, it seems to me, is knowing, at least, that they are there.

The only longish period I spent living alone was in a basement in Notting Hill. I grew so gloomily self-absorbed that all my friends began to avoid me, or maybe we began to avoid each other. Either way, it was not a good patch and I do declare I spent great tracts of it too depressed to do anything much except lie in bed. Some people fare better on their lonesome than others, of course – not all single-unit-dwellers are quite so unappealing.

Actually, it’s the single-unit men who bother me. Most particularly, the healthy, wealthy, relatively attractive heterosexual men, in their early middle age, who have somehow managed to slither through their enjoyable lives without ever being fooled into matrimony – that is to say, a lifetime commitment to somebody who probably wants to have children. It seems unimaginable that a person could go through 40-odd years without ever falling in love sufficiently to want to share their life with someone – yet these men do.

I suppose one should feel sorry for them. And I would, if they didn’t often seem so conceited. They’ve spent too many evenings with too many single women pretending to be interested in their ghastly careers, in the faint hope it might eventually pay some emotional/ procreational dividend, and they come to believe (I suspect) that their hopes and dreams really are more precious and special than anyone else’s.

The good news is, I’ve found a perfect little subterranean den for one of them. If a spell down here doesn’t send them bounding into the loving embrace of family life and matrimony, I’m not sure anything will. Because, by gum, it’s depressing.

Not on the outside, though. Ovington Square is probably one of the prettiest garden squares in Knightsbridge, barely a minute’s walk from the magnificent retail and cab-hailing opportunities of the Brompton Road, within spitting distance, more or less, of the Brompton Oratory and excellent for the Tube. It’s a beautiful square and an impressive address. To be fair, for a mere £450,000, you could hardly expect to get much of it. (To put things in proportion, there is a house for sale a little further up for £12.5m.) Yet it still seems extraordinary that anyone would consider parting with almost half a million pounds for such a miserable place.

It’s a studio flat, 437 sq ft, unlived in at the moment, with a single window that looks directly, when the door is hanging open – as it was when I visited – into a vault where the rest of the building stores rubbish bins.

There is a separate kitchen, definitely in need of a face-lift, with cheap wood-look surfaces, no dishwasher, ugly plastic tiles on the floor and no natural light. The minuscule bathroom, again windowless, is also in need of a lift. Then there is the studio itself – 17ft x 11ft, with more wood-look flooring and no fireplace.

Those are the highlights. In the middle of the studio, sandwiched somewhere between bathroom and kitchen, are frosted-glass double doors that open into what I can only describe as a coffin. The “sleeping area”, which measures 8ft 9in x 6ft 7in, and is certainly not large enough to be described as a room, offers barely enough spare space to stand in. There is a mirrored wardrobe to one side. Otherwise, everything is pine: the walls, the tiny, built-in double bed, even the ceiling. Except perhaps a sewer, I’m hard pushed to think of a place I should more hate to sleep in.

The asking price has already been dropped by £45,000. I hope it has to come down further still. Even then, it should never be recommended to claustrophobics, people with depressive tendencies or, obviously, those who cannot control themselves when confronted by expensive clothes shops. Neither will it ever be ideal for the tall, those with athletic or wider-than-average sexual partners or those who like to see daylight while they bathe or cook.

All right. I think that’s enough. The basement, 1 Ovington Square, was not for me. But if hell is, in fact, a single man in possession of a large fortune who adamantly refuses to take a wife, then this place will surely learn him.

Basement flat, 1 Ovington Square, SW3

What is it? A one-bed basement studio apartment with separate kitchen and sleeping area

Where is it?A garden square in Knightsbridge, near the Brompton Road, and South Kensington and Knightsbridge Tube stations

Who is selling it? Foxtons; 020 7591 9000, www.foxtons.co.uk

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