Police Scotland officers were blocked from boarding a US government flight at Prestwick Airport to check if it was carrying detainees as part of America’s secret torture and interrogation programme, a report has found.
The report by the Intelligence and Security Committee (ISC), a group of Westminster parliamentarians charged with scrutinising British intelligence services, found that the UK tolerated "inexcusable" treatment of detainees by the US during the war on terror following the 9/11 attacks in 2001.
Revelations in the years since have thrown light on a network of ‘black sites’ around the world where suspects were held and tortured by US intelligence agencies, as well a web of secret flights transporting detainees into captivity, including at Guantanamo Bay.
In 2013, Police Scotland opened an investigation into whether criminal offences were committed when flights stopped at Scottish airports on at least six occasions.
MPs and peers said it was "beyond doubt" that British intelligence agencies knew at an early stage that the US was mistreating detainees, and said "more could have been done" to change the US’ behaviour.
READ MORE: Government accused of 'indifference' over torture flights investigation
However, the report found no "smoking gun" suggesting officers directly carried out physical mistreatment of detainees or deliberately overlooked reports of mistreatment.
The nine-strong committee includes Ian Blackford, the SNP leader at Westminster.
In 232 cases, UK personnel continued to supply questions or intelligence to allies after they knew or suspected mistreatment, said the ISC. And in 198 cases, they received intelligence obtained from detainees who they knew or should have suspected had been mistreated.
There were at least 38 cases in 2002 alone of British officers witnessing or hearing about mistreatment. The committee rejected agencies' claims that these amounts to no more than "isolated incidents", stating: "They may have been isolated incidents to the individual officer witnessing them, but they cannot be considered 'isolated' to those in head office.
"It is difficult to comprehend how those at the top of the office did not recognise the pattern of mistreatment by the US.
"That the US, and others, were mistreating detainees is beyond doubt, as is the fact that the agencies and Defence Intelligence were aware of this at an early point."
In the report, testimony provided by Iain Livingstone, now serving as acting chief constable of Police Scotland, reveals how officers were prevented from boarding a plane on the tarmac at Prestwick to check whether it held detainees.
Mr Livingstone recalled the incident while giving evidence to the committee at the start of 2017.
“As head of Border Policing Command at the time, I did receive a telephone call from a colleague, Bob… on his very first day at Prestwick airport, when he was confronted with a particular challenge: that our colleagues in Border Force were aware of an aircraft, an American aircraft, having landed at Prestwick, having departed – I can’t remember the specific country in Africa, North Africa, if I recall – and Border Force, acutely aware of potential allegations in the past around extraordinary rendition, wished to meet that aircraft and wished to board the plane,” Mr Livingstone said.
“The chief immigration officer was seeking some guidance in terms of what can we or can we not do, and that guidance also involved them having a conversation with the Americans, who provided them with some guidance.
“And that guidance was that we can have the individuals on the aircraft come off and meet you on the tarmac; however, you cannot come on board the aircraft. So we were then presented with Bob in the distance watching Border Force engaging with the Americans on the tarmac, taking them on their word that there was no one left on board their aircraft.”
READ MORE: Scotland's part in CIA torture facing probe
In January, Police Scotland said their investigation into rendition flight stopovers was ongoing.
Reports at the time suggested classified US information requested by police had yet to be handed over, five years into the investigation.
Liberal Democrat Foreign Affairs Spokesperson Christine Jardine MP called for a full public inquiry into what British intelligence agencies knew the US torture programme.
“If it is the case that UK intelligence was aware of this reprehensible practice by a foreign agency then there must be a full inquiry, as was originally intended by David Cameron in 2010,” Ms Jardine said.