The unnamed man, who is now in his 40s, says he was attacked by a senior political figure when he was eight and knew then he worked in the 'big house' - a reference to the Houses of Parliament.
Scotland Yard has traced the alleged victim, who is a successful entrepreneur based in the United States but he has yet to make a formal statement to police.
But detectives have traced a copy of a statement he made more than 30 years ago when he was rescued from the abuse.
During his interview in 1982, the child said his abuser worked in 'the big house', which detectives believe refers to the Houses of Parliament.
The man subjected him to a horrific sexual assault and police working on the case at the time, who interviewed him, are said to have corroborated some of his evidence.
Police have visited the victim, as the Mail reported in April this year, but he refused to give a statement confirming he had been abused.
Detectives from Scotland Yard's Operation Fernbridge - the unit set up to investigate allegations of an 'Establishment' paedophile ring - have been examining the case of the alleged victim.
A detective from the US, who conducted a secondment with the team, interviewed the man on behalf of Scotland Yard earlier this year.
The alleged victim initially indicated that he would give a statement to police, only to change his mind.
Although police obtained independent evidence of the specific abuse, it was not enough to execute an arrest.
Scotland Yard has also spoken to an officer who worked on the original Elm Guest House case, and who interviewed the boy who is now in the United States.
According to the Daily Telegraph the politician's name was not included in witness statements and never put forward in case of prosecution.
It is alleged the man feared that he would be disciplined or lose his pension, so was reluctant.
Reader Comments
to our Newsletter