The British Library, beside St Pancras station, has such a forbidding brick exterior that few people other than scholars can be tempted inside. So not everyone visits the exhibition galleries, which display some of the library’s treasures but what treasures they are.

At a party thrown by the Sunday Telegraph, I was in the company of the editor, Ian Macgregor, and Claire Rayner, herself something of a national treasure, cheerfully declaring that, at 77, she was too old to have cottoned onto the Beatles; not for her, then, the manuscript of Yesterday, which was absorbing some other visitors. The Magna Carta has a room to itself.

Four of the copies made in 1215 survive, of which the BL owns two. Although the one out at the moment may be its second best, it’s the only one still bearing King John’s great seal-reduced to a wax blob by a fire in 1731.

The Magna Carta is not a human rights declaration: the clause about no imprisonment without trial appears quite low down. But inspired by the taxation imposed to fund an unpopular foreign war the document still resonates. Picturing the Runnymede confrontation between a bad-tempered autocrat and his rebellious satraps, my thoughts couldn’t help turning to Gordon Brown.