This is a welcome and most timely book. Britain’s intelligence agencies are cooperating more than ever with the armed forces in covert operations. In particular, the Secret Intelligence Service (SIS) – or MI6 as it is commonly known – and GCHQ, the global eavesdropping and cybersecurity agency, are developing a close, even symbiotic relationship with Britain’s special forces.

Since the withdrawal of soldiers from Iraq and Afghanistan, the only British troops actively engaged in military operations have been the SAS and its naval equivalent, the SBS. Yet these special forces are protected by a wall of official secrecy greater even than that enjoyed by the security and intelligence agencies. That wall may be breached only by the Ministry of Defence itself, which hypocritically encourages trusted journalists to record SAS ‘triumphs’ while at the same time allowing ministers to refuse to answer awkward questions about what Britain’s special forces have been up to.

‘Policymakers, hamstrung by austerity and public weariness of warfare’, observes Rory Cormac, ‘use intelligence resources and special forces to disrupt a range of targets from terrorists to people traffickers.’ SIS and Britain’s special forces may now be cooperating more closely than ever before, but, as this book clearly demonstrates, successive British governments, both Labour and Conservative, have used them for covert action throughout the world since the end of the Second World War.

Covert action, protected by ‘plausible deniability’, has many advantages aside from the obvious one of secrecy. It is much cheaper and less visible than conventional military action. Guided by information provided by the intelligence agencies, special forces have been – and still are – deployed in ‘pinprick’ operations to plug the gap left by Britain’s overstretched regular forces. They have helped Britain ‘punch above its weight’, masking its overall military decline.

Following the end of the Second World War, the Foreign Office and SIS officers nominally responsible to it were at first wary of those who, encouraged by the military establishment, insisted that Britain’s special forces should take on the role of the wartime Special Operations Executive, which had been tasked by Churchill to ‘set Europe ablaze’, arming resistance movements and dropping agents behind enemy lines. Although Britain did not play an active role in the undercover Continental paramilitary network known as Operation Gladio (not mentioned by Cormac), established under NATO auspices in the 1950s to organise resistance in the event of a conventional military attack by the Warsaw Pact countries, it secretly trained members of the network, which later engaged in countering left-wing parties considered ‘subversive’.

It was not long before postwar governments were persuaded that there was a role for covert joint operations, in which Britain’s special forces in effect became the armed wing of the intelligence agencies. Ministers soon gave the green light to dirty tricks, secret slush funds, coups, even assassinations.

While the Foreign Office established the shadowy Information Research Department to counter Soviet propaganda (succeeded many years later by Whitehall’s Information Research and Communications Unit to counter Islamic extremism), the intelligence agencies and special forces set up a series of secret groups and projects with sinister names, such as Special Political Action and the Joint Action Committee. In Northern Ireland in the early 1970s, the army, with the support of MI5 and the police, created a number of undercover hit squads. They included the Military Reaction Force and the Special Reconnaissance Unit. These allowed the Ministry of Defence to stick to the line, technically true at the time, as Cormac points out, that ‘no SAS unit’ was serving in Northern Ireland. The SAS presence did not become clear until the end of the 1970s, amid the ‘shoot to kill’ controversies. Later still came clear evidence of collusion between these army units, MI5, the Ulster Defence Regiment, the Ulster Defence Association, informers and loyalist terrorists in the murder of IRA suspects (and the human rights lawyer Pat Finucane).

Further afield, Britain’s special forces were deployed in Yemen, Indonesia, Vietnam (where men from the SAS and SBS were secretly seconded to Australia’s special forces) and Oman, where between 1970 and 1976 they defeated leftist rebels in Dhofar province. So concerned was SIS about Oman’s ineffective despot Sultan Sa’id that in 1970 it helped to engineer a coup in this strategically important state that resulted in power passing to his son Qaboos, who remains sultan today.

Whitehall still tries to cover up British involvement (codenamed Operation Boot) in another coup. In the late 1940s, SIS, enthusiastically backed by the Labour foreign secretary Herbert Morrison, and with the help of the CIA, began planning the overthrow of Mohammad Mossadegh, Iran’s elected prime minister, an ambition finally achieved in 1953. His sin was to nationalise his country’s oil industry, depriving Britain of lucrative profits from the Anglo-Iranian Oil Company. Despite more and more details emerging from US archives about the coup, Whitehall clings to its tired formula that it can ‘neither confirm nor deny’ Britain’s role, a response that deepens the widespread distrust of Britain among Iranians. The coup, described in some detail by Cormac, features prominently in school textbooks in Iran, though not of course in Britain.

Cormac records that after the coup, SIS launched a series of covert offensive operations in Yemen, Syria, Saudi Arabia, Iraq, Jordan, the Gulf States and Lebanon. MI5, meanwhile, helped to set up Savak, the shah of Iran’s notorious secret police. In the Congo in 1960, where the formidable Daphne Park was Britain’s spy chief, SIS actively encouraged – or, as Cormac puts it, was ‘guilty of indirect complicity’ in – the plot to assassinate Patrice Lumumba, the country’s first democratically elected prime minister. Shortly before she died, Park, who had been appointed principal of Somerville College, Oxford, a governor of the BBC and a life peer, was reported to have replied to a fellow peer who asked her whether SIS played any part in Lumumba’s death: ‘We did. I organised it.’

Cormac goes a long way towards filling a significant gap in the murky history of SIS and Britain’s special forces. I would have liked him to have gone further in confronting the problem of accountability, a crucial issue as the distinction between war and peace becomes increasingly blurred and warfare is conducted well away from the glare of the media.

In what is sometimes called the ‘James Bond clause’, the 1994 Intelligence Services Act protects SIS officers from liability resulting from actions in foreign countries which, if carried out in Britain, would be illegal. Such actions, the act says, must be authorised by the foreign secretary. Responding to reports in which I and a few other journalists described how Britain was colluding in CIA operations to render terror suspects to secret jails, where they were tortured, Jack Straw, Labour’s foreign secretary, in 2005 told MPs: ‘Unless we all start to believe in conspiracy theories and that the officials are lying, that I am lying, that behind this there is some kind of secret state which is in league with some dark forces in the United States … There is simply no truth in the claims that the United Kingdom has been involved in rendition full stop, because we never have been.’ When it later emerged that SIS had in 2004 been involved in the rendition of two opponents of the Libyan dictator Muammar Gaddafi (then Britain’s friend), including Abdel Hakim Belhaj, Straw said: ‘No foreign secretary can know all the details of what its intelligence agencies are doing at any one time.’

Handed a voluminous police file on the case, the Crown Prosecution Service (CPS) bottled out. It announced that neither Straw nor Sir Mark Allen, the senior SIS officer involved, would face charges because of insufficient evidence, although the CPS acknowledged that Allen had ‘sought political authority for some of his actions albeit not within a formal written process nor in detail’.

The Belhaj case was passed in 2013 to the Intelligence and Security Committee of MPs and peers. That body has been hoodwinked in the past by SIS and MI5. The government continues to fight demands that the committee should investigate the special forces as well as the spooks. ‘Spy chiefs are free to act nimbly in grey zones’, writes Cormac, ‘with policymakers confident they need never confirm nor deny operations.’ His book provides plenty of evidence to show why it is time this absence of accountability and freedom to break the law with impunity must end.