On 2 August 2007, Langham was found guilty of 15 charges of downloading and possessing level 5 child sexual abuse images and videos.
In 1976 also was the inception, at the Science Fiction Theatre of Liverpool, of the nine-hour stage play Illuminatus, which Langham co-wrote with Ken Campbell.
In 1977, the production transferred to the Cottesloe Theatre, London, where he took the part of George Dorn, giving a performance which Peter Hall found "extremely impressive".
Even after the original pilot was pulled from the schedules, Langham was retained for the first full series, billed equally with the then-unknown Mel Smith, Pamela Stephenson, and Rowan Atkinson.
Langham was upset at the inclusion of the sketch, which gave the team and producer John Lloyd the excuse for his replacement by support player Griff Rhys Jones.
The show only achieved cult status during its later series, and in subsequent compilation repeats, most of Langham's contributions have been cut, giving the impression that he was never a main cast member.
Also in 1979, Langham played Arthur Dent in the first professional stage version of The Hitchhiker's Guide to the Galaxy, directed by Ken Campbell.
In addition to several one-man shows, Langham counts among his stage credits Les Misérables, in which he played Thénardier in 1996; Crazy for You, for which he received an Olivier nomination; The Way of the World, The Nerd and The Pirates of Penzance.
He created the comic role of the Assassin in Blondel (co-starring Paul Nicholas; by Tim Rice and Stephen Oliver), and appears on the original cast album.
[10] Langham's former Help co-star/writer Paul Whitehouse confirmed that the character was referred to as a "peeping tom" who was prone to highly dubious sexual behaviour.
Whitehouse stated that the character was not intended to be a paedophile, nor was he personally aware of Langham obtaining such material for the development of the programme's script.
Langham also said in court that he was the victim of child sexual abuse and this caused him to look for images; Barraclough called this "pseudo-psychobabble" and the judge dismissed its legality as a defence.
On the evening that the public was made aware of the scope of Operation Ore, Langham had contacted police to report his "concern" about spam emails, with links to paedophile sites, which he said he was receiving.
The worst video was 15 minutes long and it showed in quite graphic detail the sadistic brutalisation of an eight-year-old girl in the UK, with some serious sexual offences against her".
On his release, Langham stated, "My life has been ruined, but my conscience is clear" and complained that the media "completely ignored" the court's "acceptance based upon all the evidence and expert opinion that I have no sexual interest in children".
[16] A few days after his release from prison in 2008, Langham was interviewed by celebrity psychologist Pamela Connolly, with whom he had worked on Not the Nine O'Clock News, for her UK television series Shrink Rap,[9]: 129–143 where he claimed being abused as an eight-year-old child, events which he said led to his trial and conviction.
[18] In 2011, in his first screen appearance after his release, he was cast as the lead in Black Pond, a low-budget British film directed by Tom Kingsley and Will Sharpe.
[21] He had a small, non-speaking and uncredited role as a doctor, alongside Karl Johnson, in Armando Ianucci's 2017 film The Death of Stalin, which also features Paul Whitehouse.