Two terrorists who planned to blow up planes travelling from London to North America were also involved in the abduction of a prison guard, new findings reveal.
Internal documents from the Ministry of Justice (MoJ), seen by the Sunday Times, show that Assad Sarwar and Tanvir Hussain played a "supportive" role in the plan to take Richard Thompson hostage at Full Sutton prison in North Yorkshire in 2013.
Thompson was seized by inmates Feroz Khan, Fuad Awale and David Watson – who were serving life sentences for murder – and had a knife put to his throat, until riot officers stormed the prison and freed him.
"Mr Hussain appeared to be very involved in conversations with the main perpetrators in the days leading to the hostage incident," one document seen by the Sunday Times says. "He also shaved Awale's head on the day of the incident."
Evidence was also found suggesting Hussain may have known about the attack before it took place.
One of the documents says "on collation of evidence after the incident, Mr Hussain is using the phone as the incident commences and states that he may not be able to call for a few days, indicating knowledge that something is going to happen which may later impact on their normal regime".
Khan, Awale and Watson planned on killing Thompson unless Roshonara Choudhry, an Islamist jailed for the attempted murder of Labour MP Stephen Timms in 2010, and Abu Qatada, a Salafist cleric who was in UK custody but later deported to Jordan, were released.
Thompson was held for four-and-a-half hours and was at one point told by Awale, "I've killed two people. I'll kill you."
The documents also say Hussain and Sarwar were moved from Full Sutton to another prison in the days after the incident "as intelligence indicated that they have been involved in the planning of the hostage-taking".
Sarwar and Hussain were placed in the same high-security prison after they attempted to blow up seven planes flying from London to San Francisco, Washington, New York, Chicago, Toronto and Montreal.
The plot prompted the biggest terror investigation ever mounted in the UK.
The Sunday Times said the suspected involvement of the terrorists in the abduction underlines concerns about the risk of extremists radicalising other inmates. About 130 Muslim prisoners in England and Wales have been convicted of terror-related offences.