Communications watchdog Ofcom is investigating after bad language was broadcast in Monty Python's farewell show before the watershed, even though dozens of fans complained that most of the swearing was cut.
Many of the complaints about the broadcast, which went out before the watershed on Gold on July 20, objected to "cuts" and "censorship" after some of the swearing was cut out of the programme but the censors missed some of the most controversial language.
An Ofcom spokesman said: "After receiving complaints about the broadcast of the most offensive language before the watershed, Ofcom is investigating a live performance of Monty Python on Gold."
The remaining members of the cult comedy act - John Cleese, Michael Palin, Eric Idle, Terry Gilliam and Terry Jones - got back together in London for a string of gigs at the O2 Arena, which included several near-the-knuckle routines and swearing.
The Ofcom spokesman added: "All our licensees are required to comply with our broadcasting rules, which make clear that the most offensive language cannot be shown on television before the watershed.
"As a post-transmission regulator, we are not involved in editorial decision-making and can only investigate programmes or take action against any channel after a programme's broadcast."
Monty Python's Flying Circus was made for TV between 1969 and 1974 and generations of fans can recite lines and whole sketches. The comedy troupe also made a string of hit films including Life Of Brian and The Meaning Of Life.
Sixth Python Graham Chapman died of cancer in 1989, aged 48.