Who knew that Fergie always screams on sighting a cake? This is not the Fergie who manages Manchester United, and it is said screams at his players regardless of whether any patisserie products are present. Nor is it the Fergie from the Black Eyed Peas, although Will.i.am's sidekick is eccentric enough to scream at anything at all for no good reason.

This is Fergie, Duchess of York, and while there is nothing I can find that has been written about it (I heard it mentioned on Radio 4) I don't think the cake-screaming is an OCD but something she has used as an aversion-therapy technique for a long time. Since early adulthood, Fergiana, who sources her comfort eating to the childhood trauma of her mother leaving the family home ("I took my grief and pain and ate it away"), has never set eyes on a Battenburg, a Dundee, a Black Forest, or even an Eccles without emitting a piercing yelp.

Judging by the fluctuations in girth, this method has had mixed success. One does not become a global ambassador for WeightWatchers, as she was until the organisation decided to slim its budget, without putting away one's own – and many other people's, come to that – fair share of gateaux. In fact, it could well be that WeightWatchers signed her up to buy her silence out of fear that, if this rival method to being weighed and shamed each week ever got out, it would put them out of business.

If the cake-screaming won her that prestigious post, it has cost her others. She will never, for example, be a global ambassador for Mr Kipling, even if she does make exceedingly good shrieks. And any chance she once had of fighting her financial difficulties with a job in a cake shop has vanished. Well, it just wouldn't work, would it? "Excuse me, Miss ... sorry, excuse me, Your Grace, but how much is that cake?" "Which one?" "That one there." "Aaaarghhhh." "OK, what about the one over there – the coffee and walnut one?" "Eeeeeeek!" She wouldn't last five minutes.

Still, it does suggest a lucrative commercial opportunity. Fergie could bring out her own mass-produced cake modelled on Munch's best-known painting, marketed on the theory that the scream screamed because it saw her. A cake that screams at the sight of the Duchess of York might strike a profitable reciprocal chord with a nation that would know, all too well, how it felt.