Everyone now has heard of Momentum, the successful grassroots organisation which many believe (and some fear) is taking over the Labour Party. Momentum was founded in 2015 by a Labour activist, Jon Lansman, who was formerly an aide to Tony Benn. It is currently the vehicle driving – some say fanatically – the left-wing leadership of Jeremy Corbyn.

David Blunkett, himself a veteran left-winger, is nevertheless dismayed by the success of Momentum. “The people running Momentum are modern-day Marxists,” he has written. “I’m in despair at this calamitous situation.”