It's elementary, there's nothing quite so scary as real family man
Playing a man who can, quite literally, tell a girl's measurements just from gazing into her eyes, Sherlock's Benedict Cumberbatch already had half the female population putty in his hands.
But now he's melted us right down to mush. His flirty foe was right when she told Holmes that brainy was the new sexy. But it seems that broody is the new even sexier.
When asked about his biggest disappointment in life, Cumberbatch told a newspaper this week it was "not being a dad by the age of 32''. What did the BAFTA nominated actor consider his greatest achievement? It seems his melancholy at not yet producing offspring overwhelms even his most brilliant successes: "I wish I could say children,'' the clucky thespian sighed, with a humility almost as seductive as the poetic melancholy he emits when looking down upon his baby-less arms.
Cumberbatch has built up an army of female fans - or 'Cumberbitches' - over the last year. This is a man with such intelligence in his eyes and self-assuredness in his gait that he has, with Sherlock, managed to make a sex symbol of a cold-blooded sociopath.
Faced with a chap as clever, talented and sparky as he, it is customary for a woman to smoke out his Achilles heel. We know it can often be a game changer, a ruinous revelation - an addiction to online porn perhaps, or a fervent belief that the Old Testament is fact-based reportage. When it turns out he's a man who yearns to cradle babies - well, he had us at 'Huggies'.
Of course not every woman is disarmed by a successful, switched-on man with paternal urges. I assume there are plenty who don't want kids themselves whose heart sinks when a potential partner confesses his dream to be a father.
But I suspect the vast majority are softened by a male confession of broodiness. While it might not have fitted in with their wife's or fiancé's immediate plans, the news that Russell Brand and Gethin Jones were keen to have children will undoubtedly raise their value in the singles market they've just re-entered.
It's not just the suggestion of long-term commitment which draws women to an aspiring dad, though that's the mistaken assumption of many men (except for the more savvy ones who've experienced being swamped by 'friendly' women when they take their kids to the park; a friend of mine admitted he sometimes took his wedding ring off when carrying out such duties, the bad man).
It's also the notion of a softness under the skin, an urge not merely to procreate, but to protect, nurture and teach. I'll never forget John Lydon telling me he'd trade in every minute of his state-shattering punk exploits with the Sex Pistols if he could have been a dad instead. In an instant he went from a sneering smart-arse to a man I could have loved.
Lydon also told me he loved hosting kids' parties, reminding me of another quality women love to see in the father of their children. Men seem to retain the risk-taking, thrill-seeking instincts of childhood better than women - perhaps it's true that boyhood never really leaves them.
Sandcastles are built, roller-coasters are ridden, back-garden pirates and mermaids are evoked with a gusto that mums often can't quite muster.
And there's nothing sexier than seeing a man throw off his tie to get ruddy-cheeked wrestling with an imaginary crocodile. Well, almost nothing. But other positions it would be nice to see Benedict Cumberbatch in are best left to another day.