A TV documentary about late paedophile MP Cyril Smith threatens to expose how the British establishment helped cover up his child sex crimes.
Channel 4's Dispatches, The Paedophile MP - How Cyril Smith Got Away With It, has alleged that no less than eight sex abuse crimes, including six in a children's home founded by Smith, were covered up by MI5 during the 1970s.
In a dossier that was kept hidden for four decades, eight boys alleged that Smith administered "hygiene examinations" in which he touched them inappropriately after they were stripped, massaged and physically abused.
But the claims were never investigated and Smith escaped justice. The Liberal MP was regarded as too valuable to the Labour government during negotiations for a Liberal-Labour pact to keep James Callaghan's administration in Downing Street, the programme-makers alleged.
A police office in Lancashire told the cameras that he recalled how the explosive file disappeared. Tony Robinson said he took a phone call from the secret service in 1977, which asked for the file to be transported from the safe where it was being stored to London.
The Dispatches team uncovered the file after it had been lying in secrecy for nearly 40 years.
Another former police officer told the programme that he was warned off interviewing an 18-year-old as part of a murder enquiry by Special Branch. Paul Foulston found out that the individual had been in a sexual relationship with Smith.
Foulston said: "It was quite apparent to us that they were in effect protecting Cyril Smith and not investigating him."
Assistant chief constable of Lancashire Andy Rhodes said: "The reason Cyril Smith, Jimmy Savile and Stuart Hall got away with what they got away with - serious, serious prolonged sexual exploitation of young people - was because leaders who had a responsibility to do something did not do it.
"They turned a blind eye. Buried their heads in the sand.
"There are a lot of leaders around the country becoming aware and increasing their knowledge about what sexual exploitation is all about in their areas.'
The Paedophile MP - How Cyril Smith Got Away With It is on Channel 4 tonight (Thursday) at 11pm.