British intelligence agency GCHQ is facing fresh calls to reveal the extent of its involvement in the US targeted killing programme after details of a fatal drone strike in Yemen were included in a top secret memo circulated to agency staff.

A leading barrister asked by the Guardian to review a number of classified GCHQ documents said they raised questions about British complicity in US strikes outside recognised war zones and demonstrated the need for the government to come clean about the UK’s role.

The documents, provided to the Guardian by NSA whistleblower Edward Snowden and reported in partnership with the New York Times, discuss how a joint US, UK and Australian programme codenamed Overhead supported the strike in Yemen in 2012.

The files also show GCHQ and Overhead developed their ability to track the location of individuals – essential for the targeted killing programme – in both Yemen and Pakistan. The legality of the US’s lethal operations in both countries has been questioned by international lawyers and human rights groups.

Jemima Stratford QC, who reviewed the Snowden documents for the Guardian, said: “Assuming that the documents which I have seen are genuine, in my view they raise questions about the extent to which UK officials may have had knowledge of, or helped to facilitate, certain US drone strikes which were not carried out in the context of an international armed conflict,” she said.

“These documents underline why greater transparency as to UK official policies would help to ensure legality from a domestic and international law perspective.”

Stratford published a legal opinion last year warning that UK intelligence support for lethal strikes outside traditional battlefields – such as Iraq and Afghanistan – was likely to be illegal. “In our view, if GCHQ transferred data to the NSA in the knowledge that it would or might be used for targeting drone strikes that transfer is probably unlawful,” she wrote.

Ex-GCHQ chief Sir David Omand signed a letter last November calling on the UK government to disclose its guidance on intelligence-sharing where individuals may be targeted by covert strikes. Photograph: Michael McGurk/Rex

British officials and ministers follow a strict policy of refusing to confirm or deny any support to the targeted killing programme, and evidence has been so scant that legal challenges have been launched on the basis of single paragraphs in news stories.

Commenting on the new information, Conservative MP David Davis said: “It’s no good the government hiding behind its standard security line that they never comment on security matters. The phrase extra-judicial killing is a euphemism. What we are talking about here is murder. It may be that you are murdering terrorists and the people are villains, but it is still murder. We don’t countenance murdering criminals in Britain. Why should we countenance murdering them in Yemen or anywhere else?

“It is important the government makes plain: what are the limitations it puts on the use of its intelligence, and under what statutes and on whose approval this information is shared?”

Even a former head of GCHQ has objected to Britain’s continuing secrecy over the issue. David Omand joined Davis and fellow MP Tom Watson in signing a letter last November calling on the government to disclose its guidance on intelligence-sharing where individuals may be targeted by covert strikes.

The release of the information, they wrote, would “underline the distinction between Reaper strikes by our armed forces in Afghanistan, and now Iraq, and those of other states elsewhere”.

Watson told the Guardian: “The government has always maintained we are not complicit in targeted extra-judicial killings. Any note of ambiguity identified by these documents has to be thoroughly investigated.”

The new documents include a regular series of newsletters – titled Comet News – which are used to update GCHQ personnel on the work of Overhead, an operation based on satellite, radio and some phone collection of intelligence. Overhead began as a US operation but has operated for decades as a partnership with GCHQ and, more recently, Australian intelligence.

The GCHQ memos, which span a two-year period, set out how Yemen became a surveillance priority for Overhead in 2010, in part at the urging of the NSA, shortly after the failed 2009 Christmas Day bomb plot in which Umar Farouk Abdulmutallab attempted to detonate explosives hidden in his underpants on a transatlantic flight.

Ten months later a sophisticated plot to smuggle explosives on to aircraft concealed in printer cartridges was foiled at East Midlands airport. Both plots were the work of al-Qaida in the Arabian Peninsula (AQAP), the Yemen-based al-Qaida offshoot.



GCHQ noted in the memos that the NSA’s focus on Yemen was a “great opportunity” for UK agents to focus on any leads they had in the country. Given the domestic terror threat to the UK as well as internal conflicts in the country, GCHQ has multiple reasons to be monitoring individuals in the country.



One Comet News update reveals how Overhead’s surveillance networks supported an air strike in Yemen that killed two men on 30 March 2012. The men are both described as AQAP members.

In the memo, one of the dead men is identified as Khalid Usama – who has never before been publicly named – a “doctor who pioneered using surgically implanted explosives”. The other is not identified.

In the two years of memos seen by the Guardian, this was the only specific strike detailed, raising questions as to why GCHQ’s team decided to notify staff about this particular strike among hundreds.

The files show GCHQ (pictured) and Overhead developed their ability to track the location of individuals – essential for the targeted killing programme – in both Yemen and Pakistan. Photograph: GCHQ/EPA

The Guardian asked GCHQ whether this was because UK personnel or bases were involved in the operation. The agency declined to comment, and offered no explanation as to why British staff were briefed on this particular strike.

US officials confirmed to Reuters in 2012 that there had been a single drone strike in Yemen on 30 March of that year. According to a database of drone strikes maintained by the not-for-profit Bureau of Investigative Journalism, the only incident in Yemen on that date targeted AQAP militants, causing between six and nine civilian casualties, including six children wounded by shrapnel.

Asked whether the strike described in the GCHQ documents was the same one as recorded in the Bureau’s database, GCHQ declined to comment.

The incident is one of more than 500 covert drone strikes and other attacks launched by the CIA and US special forces since 2002 in Pakistan, Yemen and Somalia – which are not internationally recognised battlefields.

The GCHQ documents also suggest the UK was working to build similar location-tracking capabilities in Pakistan, the country that has seen the majority of covert strikes, to support military operations “in-theatre”.

A June 2009 document indicates that GCHQ appeared to accept the expanded US definition of combat zones, referring to the agency’s ability to provide “tactical and strategic SIGINT [signals intelligence] support to military operations in-theatre, notably Iraq and Afghanistan, but increasingly Pakistan”. The document adds that in Pakistan, “new requirements are yet to be confirmed, but are both imminent and high priority”.

In this footage from the last months of 2014, Mohammed Saleh Tauiman, 13, interviews his brothers and sisters about their father, killed in a US drone attack Guardian

The note was written months after Barack Obama entered the White House and escalated the use of drones in Pakistan, conducting more strikes in his first year in office than George W Bush had in the previous four years.

By this point NSA and GCHQ staff working within the UK had already prioritised surveillance of Pakistan’s tribal areas, where the majority of US covert drone strikes have been carried out. A 2008 memo lists surveillance of two specific sites and an overview of satellite-phone communications of the Federally Administered Tribal Areas, in which nearly all Pakistan drone strikes have taken place, among its key projects.

British intelligence-gathering in Pakistan is likely to have taken place for a number of reasons, not least because UK troops in Afghanistan were based in Helmand, on the Pakistani border.

One of the teams involved in the geo-location of surveillance targets was codenamed “Widowmaker”, whose task was to “discover communications intelligence gaps in support of the global war on terror”, a note explains.

Menwith Hill RAF base in Yorkshire, where some of the personnel involved in the ‘Widowmaker’ programme were based. Photograph: Christopher Furlong/Getty Images

Illustrating the close links between the UK, US and Australian intelligence services, Widowmaker personnel are based at Menwith Hill in the north of England, in Denver, Colorado, and in Alice Springs in Australia’s Northern Territory.

Other Snowden documents discuss the difficult legal issues raised by intelligence sharing with the US.

A secret 2009 legal briefing suggests that British military lawyers believe that some US operations beyond traditional battlefields may be unlawful – a document that also highlights GCHQ’s efforts to operate within the bounds of the law in a complex and challenging environment.

The briefing prepared for GCHQ personnel sharing target intelligence in Afghanistan instructed them to refer to senior compliance staff before sharing information with the US if they believed it may be used for a “detention or cross-border operation”.

This, the documents states, was because the US forces were operating under Operation Enduring Freedom rules, which are less restrictive than the Nato-led International Security Assistance Force rules governing UK personnel. As a result, sharing intelligence “may result in unlawful activity” by GCHQ staff.

The Guardian contacted GCHQ with the information contained in this article, and asked a series of questions on the extent of intelligence sharing with the US in connection with targeted killing, and the legal framework for any such activities. The agency declined to comment on specifics.

The Guardian asked Downing Street why it refused to clarify any UK role in US drone strikes. A government spokesperson said: “It is the longstanding policy of successive UK governments not to comment on intelligence operations. We expect all states concerned to act in accordance with international law and take all feasible precautions to avoid civilian casualties when conducting any form of military or counter-terrorist operations.”

Asked last year about the Britain’s role in US operations outside traditional war zones, defence minister Mark Francois told parliament that “strikes against terrorist targets in Yemen are a matter for the Yemeni and US governments”. Ministers including Sayeeda Warsi have used similar language when discussing drone strikes in Pakistan.

The UK has faced previous legal challenges over the issue. In 2012, the family of a tribal elder killed in Pakistan, Noor Khan, launched a court case in England in which barristers claimed GCHQ agents who shared targeting intelligence for covert strikes could be “accessory to murder”. Judges twice refused to rule on the issue on the grounds it could harm the UK’s international relations.

• Alice Ross formerly worked on The Bureau of Investigative Journalism’s drones team.