Finally, the boy's father says he was informed by Scotland Yard that the abuser had been sent to prison for assaulting his son, and that no further action was needed.
However it was only years later, the family claim, that they discovered the culprit's true identity. They then discovered Morrison had never been jailed for any crime, and that police had apparently duped them into dropping the allegation.
The man, now a married businessman, is the first of Morrison's alleged victims to speak publicly. His story is backed up by his parents and is being investigated in Operation Fairbank, set up by the Met two years ago to probe suggestions that high-profile political figures had been involved in organised child sex abuse.
He is now preparing to take legal action against the force, who he claims "hushed the whole thing up".
Morrison was Thatcher's trusted parliamentary private secretary and deputy chairman of the Conservative Party. In 1990, he led Thatcher's disastrous leadership campaign team.