Posturing by a previous home secretary over the death of a policeman eventually led to the abolition of the mandatory death penalty for murder. David Maxwell-Fyfe's refusal to pardon Derek Bentley led to an injustice so grave that something had to give, though not before the state had strangled a mentally disabled teen who never fired a shot. Yesterday another home secretary, desperate to make peace with the bobbies who booed her last year, proposed a new mandatory sentence for killing a cop, which might be described as death by incarceration. The idea of automatic life without any possibility of parole brought Theresa May a brief moment of favour at the Police Federation, but as policy it is objectionable in principle and will also prove ineffective in practice.

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