On quiet nights in the BBC Radio newsroom, a former colleague of mine used to supplement his income by churning out features for an old-fashioned news agency. The agency was more interested in quantity than in-depth research, and one of these features – I forget if my friend was responsible – concerned the alleged extreme rarity of sinistral, or left-coiling, whelks. A regional newspaper, possibly in Grimsby, went big on the whelk story, inviting readers to submit samples of this exceptional shell. The upshot was an angry phone call from the editor of the paper to the boss of the news agency casting doubt, in forcible terms, on the veracity of the story and demanding to know what he was supposed to do with the pile of ‘effing left-handed whelks’ on his desk.

The reason for the scarcity of sinistral common whelks, I learn from Helen Scales’s study of seashells, is that it is