Friday morning of 12th August, John Edward 'Jack' Witney (36), John Duddy (36) and Henry (known as Harry) Maurice Roberts (30), are cruising the streets of west London looking for three high performance cars to steal as part of a robbery they're planning at a Northolt engineering works. When their scruffy blue Standard Vanguard estate car is routinely stopped, Harry Roberts pulls his shotgun and fires, in cold blood, at the three policemen. Massacred in the line of duty.

The crime, the criminals, the victims and their families, the hunt for the three murderers, the establishment, press and public reaction, the trial, the cultural and political context and the long aftermath are all set out in compelling narrative detail. The book will explore the territory of the crime itself, touching on the social and political context of 'the swinging 60s' and the stories of the three men involved (one went to prison for 25 years although he took no part in the actual shooting, was released on appeal only to be murdered in his Bristol flat a few years later, another died in Parkhurst), with the emphasis on the biography of Harry Roberts and the 48 years he spent in prison.

What could possess an apparently rational and sane man, albeit an habitual criminal, to calmly, and without a second thought, commit such a brutal and ruthless act? And if Harry Roberts is not in some way clinically insane, how does he reconcile his killing? How has he come to terms with it? What kind of man is he? How can an ordinary person understand what he did? Should he be forgiven?