Diverting money from aid to the military is a grim expedient in a crisis that will surely define this prime minister’s legacy

British politics is having one of its periodic outbreaks of polarised consensus. This is the paradoxical condition that occurs from time to time when the ruling party and the official opposition are forced by circumstance to have the same policy, while compelled by traditional enmity to resent the convergence.

The pressure on Keir Starmer to raise defence spending to 2.5% of gross domestic product has been building steadily in recent months, and independently of Tory demands that he do it.

Rafael Behr is a Guardian columnist