Unremarked, in many redoubts of the nation, in Rochdale, Watford and Sheffield right now, the nation’s most visceral and pointless political rivalry is taking place. Though the political parties have swung to the extremities of the spectrum, the Tories taken in by Brexit and Labour by Corbyn, their rivalry is a small matter besides the narcissism of small differences between two parties that ought to hang together. There is nobody a Labour activist likes to disparage more than a Liberal Democrat. It is the most puzzling and tenacious antipathy in politics.

Before examining why this might be, and its deleterious consequences, let’s just note the proximity of these parties. Early Labour MPs often stood on a coalition ticket with the Liberals. They were rivals but…