In Anthony Trollope’s 1876 novel The Prime Minister, the title role is taken by Plantagenet Palliser, the Duke of Omnium. Those were the days when the governing party could ransack the upper house for talent if it had no suitable candidate in the Commons. The temptation to revive Trollope is the fundamental fact to keep in mind when considering Theresa May’s announcement, made during her trip to Japan, that she intends to fight the next general election as leader of the Conservative Party.

In 1963 Alec Douglas-Home renounced his peerage shortly after he became prime minister. In 1902 the Marquess of Salisbury was the last prime minister to lead a government from the Lords. The 7th Marquess of Salisbury sits in the Lords as