‘Often it’s over nothing,’ he says, when I ask about what he and St Giles see as common causes of knife attacks. ‘Impulse control, money, prestige. The stimulus can be minimal and the action is horrendous. Occasionally, something more significant, some sort of long, deep-seated issue. But more often than not, it’s trivial — he said this, she said that. A lot of this stuff seems to be an insanely cheap tariff for a life.’