Married to a public-school man (I almost said boy) for many a long year, I can’t bring myself to disqualify politicians for that crime alone. But during last week’s party leaders’ debates I did detect the tang of the Shell, as I think they call upper forms at Westminster, when I heard Nick Clegg say to Ed Miliband: ‘I will leave that pious stuff.’ It echoed from Tom Brown’s Schooldays (at Rugby) long ago or that weird novel The Hill (Harrow).

Mr Clegg’s cosmopolitan background looks resistant to establishment conventions, yet, for that very reason, he takes some on board without noticing. It is no coincidence that the Westminster term beginning in April is called Election Term. Well, it may be a coincidence, but another one is that the examination for scholarships is called the Challenge, which used to be entirely oral, with candidates interrupting or challenging each speaker. Next week’s television debate is for challengers.

As for Mr Clegg’s accusation of being pious, he went on: ‘You crashed the economy. Say I’m sorry for crashing the economy.’ It was as though he had a younger boy’s arm up behind his back and was wringing an apology from him. Yet the imputation of piety was strong rhetoric. No one likes a pi dog. Winchester, though, not Westminster, is credited with coining pi as a pejorative term. ‘He’s very pi now, he mugs all day. He pi-jawed me for thoking,’ says an edition of the Winchester Word-Book from 1891. It might have been in use much earlier. After all, thoke is found elsewhere in the 15th century, though noted at Winchester only in that word-list from 1891. In the world, thoke seemed to mean ‘moist’, like a bad fish, but at Winchester ‘idle’ or ‘lie-a-bed’.

Never mind that to be pious was counted the highest virtue in the pagan world of Rome. It described the love of a parent or a child, and hence, in Christianity, the love of a creature for the creator. From the 17th century onwards, pious often came to be paired with fraud or hypocrite. Pious words belied wicked deeds. So, in a war of words, the accusation of being pious is a powerful challenge.