During the late 1980s a serving member of Margaret Thatcher’s cabinet told me that the prime minister was mad, quite mad. As I recall, this minister had just had a bruising confrontation with the lady about the poll tax.

He was soon to be proved right in his prediction that a tax imposing the same burden on the dustman as the duke could destroy her premiership. All the same, I was a bit shocked that a cabinet minister would share with a journalist such concern about the prime minister’s mental balance.