It should be called The Traitors’ Club. It opens in the cloisters of Cambridge University, moving to the bustling insides of spy central, Century House beside Waterloo station, and then to the elegant, cushioned, gentlemen’s clubs of Knightsbridge and Pall Mall.

The script sketches the treachery and betrayal of the five university spies led by Kim Philby, but the arc of it is about another Cambridge man, not part of this class-ridden clique, and how he was the most successful of them all. Caught and jailed, but five years on sprung by two anti-nuclear pacifists with a ladder made of knitting needles, he was then taken to Russia in a camper van and with the connivance of a career Scottish criminal.

Films often claim to be based on fact, while they usually treat it as a point of departure. The only fact in doubt in this potential screenplay is whether safecracker Paddy Meehan revealed to the KGB how to spring George Blake from prison, or whether he tried to warn the British secret services that this was planned, and by Soviet agents within their own camp.

Blake died last week aged 98. Whether he was responsible for betraying 40 agents or double agents, or 400 – David Cornwell aka John le Carré was one of them – he was certainly guilty of passing on every piece of sensitive information that crossed his MI6 desk and would be useful to the Soviet Union. That included a joint MI6 and CIA tunnelling operation under the Berlin Wall which tapped into Russian and East German military intelligence communications. Alerted, the other side for years sent back torrents of disinformation, together with a few harmless nuggets to avoid suspicion.

Blake’s background was radically different to the private school-educated Cambridge Five – Philby, Guy Burgess, Donald Maclean, Anthony Blunt and John Cairncross. He spent most of his boyhood in the Netherlands and after his father, an Egyptian Jew, died was sent to Cairo, to cousins, one of whom was a communist. He returned to the Netherlands when Germany invaded the country in 1940 and became a teenage courier for the resistance.

Although he was briefly interned he was released because of his youth and he fled the country disguised as a monk, via France, Spain and Gibraltar, joining his mother and sisters in Britain and taking the name of Blake, rather than Behar. He was recruited by MI6, largely because of his language skills.

In 1948, under the cover of the post of British vice-consul, he was sent to head a new station in Seoul with instructions, according to MI6’s official history, to target northeast China and communist activities in Korea. He was captured after the outbreak of the Korean War and it was his two years in a North Korean prison where he read Das Kapital among other books, that his faith in communism was locked in. Whereas the Cambridge Five were anti-fascists who passed on information to the USSR principally in wartime, Blake became a devout believer in communism.

He had previously read Russian and Marxist literature at Cambridge, where he had been sent by MI6 in 1947 to learn Russian, but it was this prolonged exposure to the literature in his jail cell which turned him. He said later: “If I had read Marx in a different setting, if I had been living comfortably in a flat in London, maybe I would have come to the same conclusions. But I might not have taken such drastic steps.”

He was himself betrayed in 1961 and convicted of spying after a trial largely in secret. He was given vicious maximum sentences, consecutive rather than concurrent, going down for 42 years.

It is here that Patrick – universally called Paddy – Meehan enters the tale. He had been in prison for most of his adult life, having graduated from Borstal, picking up safe-blowing skills along the way. In 1955, he masterminded the escape of Terry “Scarface” Martin from Peterhead prison and did it himself in 1963 when serving an eight-year sentence in Nottingham Prison, scarpering during a cricket match.

Using a false passport he made his way to East Germany (he had briefly been a boyhood communist) where he was held for 14 months. He was interrogated by the KGB and, according to him, he passed on information about how Blake could be broken out of prison. Later, in jail in the UK, he claims he was visited by a British secret service agent called “Hector” who, he believed, was probably a KGB mole.

It was the Blake imbroglio which was to blame for what was to come, at least that was Meehan’s belief, or perhaps cover story.

In 1969 – three years after Blake had made an unlikely escape from Wandsworth Prison – and as he was being sentenced for murder in the High Court in Edinburgh, Patrick Connolly Meehan stood to attention in the dock and said: “I am innocent of this crime. You have made a terrible mistake.”

The crime was breaking into the Ayr home of elderly bingo hall owner Abraham Ross, stealing jewellery, and torturing him and his 72-year-old wife Rachel. The couple were left tied up for 30 hours, proving too much for Rachel, who died in hospital.

Meehan’s defence (his junior course was John Smith, later to become Labour leader) was that he and his criminal cohort, James Griffiths, had passed through Ayr on their way to case a place in Stranraer. Meehan had no convictions for violence although Griffiths had many. However, Meehan’s alibi and corroboration died abruptly in a hail of bullets.

Police traced Griffiths to the west end of Glasgow where he opened fire and 13 people were shot and wounded, including police officers. But the only person to be killed was Griffiths.

Meehan had another special defence, alleging that two Glasgow thugs, Ian Waddell and William “Tank” McGuiness, were the guilty pair. Five years on, in 1974, Waddell turned up at the Daily Record and confessed, also giving information only the raiders could have known.

Like the other suspects in the case, he was to die violently, murdered in Glasgow in 1982. McGuinness, who had confessed to his lawyer Joe Beltrami that he was the other guilty one, died in a brawl in March 1976 in Janefield Street near Celtic Park.

On the day McGuinness died, family members contacted Beltrami saying that he had previously told them he had committed the Ayr murder, which allowed the lawyer to break his privacy commitment. Within months Meehan was given a royal pardon and a cheque for £50,000 was on its way to him. But that wasn’t enough. He believed not just that he had been fitted up by police for the Ayr murder – and there’s little doubt now that evidence was planted on him and witnesses were coached and lied to – but that the orchestrators were the UK secret services over the Blake affair.

Five years after his conviction Blake escaped from Wormwood Scrubs – in what seemed such an unlikely and, indeed, hand-knitted breakout – with the help of two radical anti-nuclear campaigners, Mike Randle and Pat Pottle, and an Irish petty criminal, Sean Bourke.

A walkie-talkie had somehow been smuggled inside and, when the other prisoners were at a weekly film show, Blake smashed a window, climbed out, slid down a porch and ran to the perimeter wall. Bourke threw the flexible ladder made of knitting needles over the wall, enabling Blake to climb over and join the CND escape crew.

He was put up in several houses of sympathisers until Randle hastily arranged a family holiday, hid Blake under the bunks of his camper van, and drove to East Germany where he dropped him off at a roadside.

Twenty years later, when Randle and Pottle’s names came out publicly – although they had been known to the authorities since the escape – clamour for prosecution by Tory MPs and the right-wing press led to charges but, in the same courtroom Blake had been sentenced, they were unanimously found not guilty.

There should be a dramatic denouement to this, but almost 60 years on from Blake’s conviction and Meehan’s claim of conspiracy there still isn’t one. The safebreaker was never interviewed about his claim to have tipped off agent “Hector” about the escape and Meehan died 26 years ago. The Home Office, despite Freedom of Information requests, is still refusing to make public the Meehan files on grounds of national security.