Britain’s Secret Intelligence Service (MI6) and the US Central Intelligence Agency (CIA) toppled Iran’s secular, anti-colonial prime minister, Mohammad Mosaddeq, in August 1953. The coup d’état marked an important turning point for Iranian politics: it returned the pro-Western Shah Reza Pahlavi and strengthened the West’s short-term position in the Middle East. Yet, in a glaring example of blowback, it also set Iran on a path to dictatorship that would eventually sow the seeds of the 1979 Islamic Revolution, forever haunting Iran’s relationship with the West.

The role of British and American intelligence is not in doubt. In the US, releases to the National Security Archive, material from the CIA and State Department and even memoirs provide most of the story. Yet in Britain there is still a reluctance to acknowledge what is effectively an open secret in Washington, London and Tehran.

The British government still maintains a wall of silence. Requests under the Freedom of Information Act (2000) for files on Britain’s policy towards Mosaddeq’s government met with a series of exemptions; information supplied by Britain’s spies (Section 23), national security (Section 24) and international relations (Section 27) were all used. Whitehall maintains a ‘neither confirm nor deny’ stance, despite growing evidence of Britain’s involvement in foreign archives. This is in line with departmental records policy. Despite the release of documents on Operation Valuable – Britain’s abortive anti-communist operations in Albania – and an SIS plan to disrupt illegal immigration in Palestine (Operation Embarrass), Whitehall remains reluctant to release details of Britain’s postwar special operations into the 1950s. SIS also works closely with ‘partner-departments and agencies’ to ensure a history that ‘does not compromise national security’.

Britain has always been sensitive to claims of dabbling in Iranian politics. In October 1978, with the US State Department poised to release a new volume of its Foreign Relations of the United States (FRUS) series covering the Mosaddeq period, Washington was keen that ‘HMG would be consulted’. US officials made it clear to their British counterparts that, if released, ‘there would be some very embarrassing things about the British in them’, but, luckily for London, US officials were happy to ‘sit on the papers’. US officials did not release a heavily redacted FRUS volume on 1950s Iran until 1989, prompting Congress to pass legislation that FRUS should be ‘a thorough, accurate, and reliable documentary record’ of US foreign policy. In 2011, the CIA released extracts from an in-house history of TPAJAX – the CIA’s codename for the coup – and a ‘retrospective’ FRUS volume was finally released in June last year. The British government was not involved, despite at least ‘two efforts to promote a joint U.S.-British project on Iran, including one through the British Foreign Office’.

Yet the British government is in danger of appearing a Cnut-like figure, trying to hold back a flood of information on the coup that never was – at least officially in British government circles. In 2000, Secretary of State Madeleine Albright even came close to apologising, admitting the coup was ‘clearly a setback for Iran’s political development, and it is easy to see now why many Iranians continue to resent this intervention by America’. More recently, President Obama pointed to America’s role in ‘overthrowing a democratically elected regime in Iran’. By contrast, Britain’s Foreign Secretary Jack Straw has been a lone voice, telling the Foreign Affairs Select Committee in 2006 that British and American spies had undermined a ‘perfectly democratic prime minister’ and later referring to the many British ‘interferences’ in Iranian politics.

Yet stonewalling has done very little to hide Britain’s role (referred to as Operation Boot by SIS). As early as 1979, the CIA’s Kermit Roosevelt, who ran the operation, published a memoir, Countercoup, citing Britain’s support. Britain’s own Christopher ‘Monty’ Woodhouse, a former SOE officer and SIS’s station chief in Tehran, who, like Roosevelt, was an instrumental figure, provided more details three years later in his account, Something Ventured. Woodhouse’s private papers and a 200-page internal CIA history were leaked to the New York Times in 2000. They included a ‘London’ draft of the plan and claimed it was Britain who pushed for a ‘joint political action’ to remove Mosaddeq in late-1952. The history even names SIS and Foreign Office officials involved in the coup.

New documents now show that Britain played an instrumental role in the planning phase, even if it was the CIA (using British assets on the ground) that eventually implemented it. Mosaddeq’s nationalisation of the Anglo-Iranian Oil Company in March 1951 set Iran on a collision course with London. Quickly ruling out military force, Britain pushed for ‘political’ action. From Washington, the proposal was viewed with alarm; any attempt to remove Mossadeq would, the State Department warned, likely increase his support, lead to a counter-coup compromising the Shah and undermine Britain’s already dwindling influence in the region. The US response was ‘chilly’. But Britain was undeterred and continued to push for Washington’s support in bringing Mossadeq down, first presenting plans in October 1952 leading to ‘tentative and preliminary’ discussions between the CIA and SIS. Rather than push Britain’s concerns about Iranian oil and commercial interests, the plans played on Washington’s fears of ‘Communism in Iran’ – even if the threat was minimal. By March 1953, thanks in part to Britain’s pandering to US fears, the State Department had come on board. During talks with the British Foreign Secretary Anthony Eden, US officials were ‘more receptive’ to a coup, seeing Mossadeq as a ‘source of instability’. ‘Mossadeq had to go’, a CIA internal history made clear.

Britain’s ‘neither confirm nor deny’ stance fools no one – it is an open secret. Certainly, Britain’s relationship with Iran remains a complex one; a 2015 nuclear deal struck between Iran and the US, China, Russia, Germany, France and the UK hangs in the balance, but it is unclear how British documents – on a coup we already know about thanks to official US sources – could really affect it. Iranians are already well informed about Western meddling in their country. It is also clear that Britain’s attempts to hide its part in Mosaddeq’s fall – as in other areas – has been compromised by Allied governments, former spies and the press. Certainly, not everything needs to be revealed. Tradecraft, agent identities and inter-governmental discussions should remain secret. But trying to pretend that Britain did not play a role is ludicrous. Surely the British government needs a new proactive release policy to provide Britain’s side of the story.

Dan W.B. Lomas is Lecturer in International History at the University of Salford.