There comes a time in a sex god’s life when his most intimate dimension (and I don’t mean his credit limit) becomes a matter of earnest public debate. It happened recently to Jude Law, when long-range paparazzi photos of him changing into his swimming kecks were circulated on the internet, and across the world discussions ensued as to whether his equipment comprised more of a chipolata than the full Toulouse.

Law probably has bigger (ha, ha) problems to worry about at the minute than public opinion about the size of his favourite part, but he is bound to be a little (ho, ho) concerned when, with millions of people giggling over it, it has been reported that Anna Wintour chucked him off the cover of the new US Men’s Vogue in favour of George Clooney.

Coincidentally, Law’s penis isn’t the only one to have been on the news agenda this summer, the heaviest on willy stories since 2000, when a debate raged as to the size of Jamie Theakston’s little Jamie after a former lover carelessly hinted that he was hung like the proverbial hamster. For the Rolling Stone Keith Richards has just claimed that rocking grandad Mick Jagger is not as well endowed as his supershagger reputation would have us believe. “His cock’s on the end of his nose,” Richards said. “And a very small one at that. Huge balls. Small cock. Ask Marianne Faithfull.”

What exactly is the deal on penis proportions, then? Is there any relationship between sighs (female) and size (male)? And is there any scholarly evidence of an inverse connection between ownership of a Porsche and penis size? Here is what we know for certain. First, even the worst a man can have — the most measly, sub-Jude, sub-Mick, sub-Jamie earthworm — would be the envy of the most priapic ape or big cat. The human penis is enormous in proportion to the rest of his body, dwarfing by far that of the gorilla, whose organ is a puny 2in erect. Only the barnacle, improbably, has a larger penis in relation to its body size than we do. (Owing to the barnacle’s sedentary lifestyle, its penis has to be capable of searching the area around it to find a receptive female. It also throws its penis away once a year and grows a new one, much like Law and Jagger must feel like doing right now.)

Second, almost all heterosexual women, a) like the feeling of being penetrated by a penis, and (within reason) the bigger it is, the more pleasurable is the feeling, but at the same time, b) will never achieve an orgasm solely as a result of penetration, however big or small the instrument in question. Without the judicious and skilful use of fingers, tongues, vibrators or other such items, the most splendid penis in the world won’t normally do a lot to satisfy a girl. Sexual pleasure tends to be the result of a range of favourable circumstances, of which penis size is way, way down the list, behind mental attraction, romantic setting or some other turn-on factor, which can range from doing it in an office stationery cupboard to doing it with someone “forbidden”, such as a horny plumber, an admired celebrity or a plain old millionaire.

Third, in the penis field, there is size and there is size. Willies have two dimensions — length and width, and it is width that is the critical factor. Even the snakiest chipolata (and it was my womenfolk’s view that Law’s, while of respectable length, is a little on the slender side), won’t reach the parts of a lady that a fatter, stubbier device will.

The reason we know that penis size isn’t a deal-breaker is the fact that there are men on the planet with undersized willies. If women were only interested in blokes with chunky appendages, small ones would have been bred out of the population generations ago as women voted with their knickers. Evolution would have seen to it that men with thick ones had more lovers and more children, and so male appendages would, accordingly, have got thicker down the generations.

Over the millennia, however, men have generally been able to make up for any deficit in their penis size with such attractive attributes as charm, kindness, power, brains, fame or wealth, while oafs with big willies but no idea what to do with them have consistently failed to attract the tastiest females on the market.

It’s often said that while men are idealists when it comes to sex, women are pragmatists, ready to swap the transient pleasures of a fab penis for more tangible benefits to themselves and their children accorded by a man who is kind, funny, rich or a combination of these.

That is the reason you so often see amazing-looking women with weedy men who look unlikely to possess much inside their Y-fronts. It’s also the reason the likes of Law or Jagger, even if they fear they have the kind of meagre dong that makes a girl want to cut straight to the cigarette, need not worry too much. They stand as much chance as the rest of us of finding girlfriends.

Times recommends

• Are eldest children really a cut above?
• Peaches Geldof: censored
• Top 10 style-setting films of all time