By-elections are not what they used to be, aficionados complain. There are fewer of them, partly because better pensions mean MPs can often afford to retire instead of hanging on until they die; and in recent years, the contests have rarely been close and thus have attracted little media attention.

The Crewe and Nantwich by-election on May 22 looks like an exception. There is a good chance the Conservatives will achieve the 8 per cent swing needed to overturn Labour’s 7,000 majority and record their first by-election gain since Mitcham and Morden in 1982.