On the eve of the invasion of Poland in 1939, German generals warned their men to be on guard against “acts of terror”. That these “terrorists” were Poles defending their homeland against desperate odds mattered little to the soldiers of the Third Reich as they put the last restraints of international law behind them. We used to think one man’s terrorist was another man’s freedom fighter. No longer, according to the British government: it knows for sure who the terrorists are. Unfortunately, its moral certainty is matched only by the lethal vagueness of its proposed new terrorism bill. Fortunately, the House of Lords has again voted down its proposal to create a new crime of glorifying terrorism. The assumptions behind this idea in particular are flawed and need a rethink.

Why a fourth new anti-terrorism bill in six years when the UK managed with fewer than that for most of the 20th century? After all, the government accepts that its current definition of terrorism is so poorly drafted that it will have to be reviewed. The reason seems to be that it has, as have other governments, decided terrorism is fanned by irresponsible imams and inflammatory videos. While many inter­war states happily jailed teachers and journalists for infecting the young with communist ideas, the postwar era’s human rights culture raised the bar on thought crime, frustrating politicians and police. Definitions of incitement currently require proof of intent; the proposed legislation aims to relax this to make prosecution easier.