Back in England from the US last year, I took a late train from London to Norwich, where I found a crowd of people waiting apparently docilely for non-existent taxis. A young couple, with startling insouciance, jumped the queue. For a while nobody said a thing. Then, catastrophically, someone complained. In a flash, sides were taken, vicious denunciations issued.

A mystifying operetta of obscenity, threat and barely suppressed violence ensued, complete with its leading players and aghast but passive chorus (played out on an exquisite stage of vomit and broken glass). All this because some poor soul had meekly invoked what is, by repute at least, the most cherished law of British decorum.