An allegation in an MI6 report about Iraq’s supposed chemical weapons capability before the 2003 war to remove Saddam Hussein appeared to have been lifted from a Hollywood film, according to the Chilcot report.

A section of the inquiry’s findings about the build-up to the conflict in the autumn of 2002 found that MI6, formally known as the Secret Intelligence Service or SIS, feared a source might have taken inspiration from The Rock, a 1996 thriller starring Sean Connery and Nicolas Cage.

The report details how MI6 sent information to “a small number of very senior readers”, including Tony Blair and the then foreign secretary, Jack Straw, on 11 and 23 September 2002.

Based on what MI6 called “a new source on trial with direct access”, this alleged that Saddam’s government had accelerated the production of chemical and biological agents, and in particular that chemical agents might be carried in glass containers.

After some discussion on the reliability of the new source, in early October MI6 was questioned directly about this idea. The report says: “It was pointed out that glass containers were not typically used in chemical munitions; and that a popular movie [The Rock] has inaccurately depicted nerve agents being carried in glass beads or spheres.”

MI6 accepted this possible flaw to the intelligence, the report adds: “The questions about the use of glass containers for chemical agents and the similarity of the description to those portrayed in The Rock had been recognised by SIS. There were some precedents for the use of glass containers but the points would be pursued when further material became available.”

Chilcot’s team describe further doubts about the anonymous source’s reliability, noting that Sir Richard Dearlove, the then MI6 chief, was “following progress of the case”.

The report adds: “By 6 December, questions were being asked within SIS about whether there was any further reporting. It was suggested that that meant ‘a health warning’ on material from SIS’s source. Following further contacts, doubts were expressed on 9 December within SIS about the reliability of the source and whether he had ‘made up all or part of the account of his dealings’ with the sub-source.

Nonetheless, in December Straw asked Dearlove’s team about the possibility of this mystery source “producing silver bullet intelligence” to guide UN inspectors to weapons of mass destruction in Iraq.

The response came that the sub-source did exist, but the main source “may not have written up the intelligence in the manner which was being claimed for him”.