During his lifetime Cyril Smith was one of the UK’s best-known politicians. But a new investigation shows that security services held on to a file with evidence of the Liberal MP’s child abuse.

Watch the full report from Dispatches at 11pm on Channel 4

Cyril Smith, the Rochdale MP who died in 2010, was a larger than life figure.

His jocular personality and his regular appearances on chat shows made him one of the best-known politicians in the country.

But an investigation by Channel 4’s Dispatches programme shows that UK security services held on to evidence of the Liberal MP’s child abuse.

Ready to prosecute

In the late 1960s Lancashire police carried out several investigations into Smith’s behaviour, compiling an 80-page file. The suggestion is that police were ready to prosecute.

However, veiled threats from local liberals meant the case was dropped and the file locked away in a safe at Special Branch, which has responsibility for national security. Labour MP Jack McCann, Smith’s predecessor as MP for Rochdale, also spoke to the DPP on Smith’s behalf.

By 1977, the Liberal party was the junior party in a pact with the country’s ruling Labour party. MI5 now also took an interest in Smith’s background.

Former Special Branch detective Tony Robinson told Dispatches he was contacted by MI5, who requested he send them the file by special courier. By now Lancashire police, Special Branch and MI5 knew about the allegations.

Lord Steel, who as David Steel led the Liberal party between 1976 and 1988, says he asked Smith about the allegations of child abuse and accepted his denial of wrongdoing.

Read more: The Past on Trial

Young victims

In Rochdale, Smith set up a hostel, Cambridge House, supposedly to help boys in need.

Dispatches spoke to one man, Kevin Griffiths, a former resident at the hostel, who first told the police about the Rochdale MP’s behaviour.

Mr Griffiths recalls how, on one occasion, he stood naked in front of Smith “and he ran his hands all up and down my thighs, inside my legs, and touched my private parts”.

Smith went on to help set up another institution in Rochdale, Knowl View School, for which he held a set of keys. It was there that Chris Marshall, then eight years old, became Smith’s youngest known victim.

And the Metropolitan police have confirmed to Dispatches that during the 1980s Smith was a visitor to the Elm guest house in south west London, where a paedophile ring was reported to have been active.