[3] On 12 August 1966, a Metropolitan Police crew in an unmarked Triumph 2000 Q-car, registration plate GGW 87C and call sign Foxtrot One One, was patrolling East Acton (although the incident was always reported by the media as occurring in Shepherd's Bush) in West London.

The officers spotted a battered blue Standard Vanguard estate van, registration plate PGT 726, parked at the roadside with three men sitting inside it.

Since escapes were sometimes attempted from the prison with the assistance of getaway vehicles driven by accomplices, the officers decided to question the occupants.

DS Head and DC Wombwell exited the car and walked over to the van, where they questioned Witney about the lack of a tax disc.

However, as he did so his front seat passenger, Harry Roberts, produced a Luger pistol and shot DC Wombwell in the face at point blank range, killing him instantly.

John Duddy, the back seat passenger, also got out, grabbing a .38 Webley Service Revolver from the bag next to him (which also contained a third gun).

Initially Witney claimed that he had sold the van for £15 to an unknown man in a pub earlier in the day, but confessed on 14 August, admitting what had happened and naming his accomplices.

[7] After meeting his common-law wife for money Roberts moved through Epping Forest then used a tented camp to hide out in Thorley Wood near Bishop's Stortford in Hertfordshire to avoid the huge manhunt.

Until the cold winter weather set in he used his military training (he had served as a soldier during the Malayan Emergency) to avoid police capture for three months.

He was finally arrested on 15 November whilst sleeping in a disused airfield hangar on Blount's Farm, Sawbridgeworth near Bishop's Stortford.

Roberts pleaded guilty to the murders of DS Head and DC Wombwell (but not that of PC Fox), while the other two defendants denied all charges.

On 12 December 1966, after a trial lasting just six days, the three men were convicted of murder and possession of firearms and sentenced to life imprisonment.

[13] With Duddy and Witney having both died, Roberts was still imprisoned more than 30 years into his life sentence, as one of Britain’s longest serving prisoners.

Roberts hoped a final hearing would find that, now in his seventies and having spent more than half of his life prison, he was no longer a risk to the public and that he would be granted parole.

The daughter of one of the murdered police officers, PC Geoffrey Fox, said she was "sickened" to learn that Roberts was to be released without any prior warning.