A former senior cabinet minister is now the subject of a rape allegation currently being considered by the Crown Prosecution Service. Police investigating possible child abuse at the Elm Guest House in West London have submitted a file on the former minister, and the CPS is expected to come to a decision over the matter during the summer. The claims are not believed to relate to the abuse of minors at the guesthouse, and the alleged victim was over the age of consent.

The allegation follows evidence given to the Metropolitan Police’s Operation Fernbridge, which is investigating claims that a well-connected paedophile ring was operating from a guesthouse in Rocks Lane, Barnes, south-west London, in the early 1980s. The inquiry has been examining hundreds of leads submitted to it after a politician claimed that a historic paedophile ring with connections to Downing Street had been in operation there. The extent, breadth and wide timeframe of the claims led police to look beyond the Elm Guest House’s allegedly dark epoch and beyond the abuse of children.

Police have been looking into claims that young boys from the Grafton Close care home, run by Richmond council, were sexually assaulted at the guesthouse – now a block of respectable flats. It is alleged that the boys were taken to organised parties at the house attended by prominent people, where they were made to dress up. The parties were often “Kings and Queens” themed, a practice begun around the time of the Silver Jubilee in 1977.

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The lack of charges relating to the guest house has given rise to counter-claims of “conspiracy theories” and cover-ups. But in January, The Independent on Sunday revealed that the disgraced Liberal Democrat politician Sir Cyril Smith, who for decades abused children without ever facing justice, was a regular visitor to the Elm Guest House.

The revelation came after police raided the house of one childcare worker and seized documents said to contain the names of some of those who stayed at the guesthouse. Those on the list also included prominent politicians, judges and celebrities.

The Fernbridge investigation came in the wake of the allegations surrounding the TV presenter and DJ Jimmy Savile.

In October last year, Tom Watson MP told Parliament that an evidence file on Peter Righton, a former child care worker convicted of importing illegal homosexual pornography in 1992, contained “clear intelligence of a widespread paedophile ring”. At Prime Minister’s Questions, he said: “One of its members boasts of a link to a senior aide of a former prime minister, who says he could smuggle indecent images of children from abroad.”

Scotland Yard is still investigating those claims, as well as suggestions that its officers failed to carry out a proper examination of child abuse claims in Richmond in 2003, when the Independent Police Complaints Commission received allegations from a concerned council worker.