Former Tory MP Neil Hamilton and his wife Christine have been arrested following an allegation of serious sexual assault, police sources said tonight.
The couple attended a London police station by appointment where they were arrested and are currently being questioned by officers.
A Scotland Yard spokesman said: "A 52-year-old man and a 51-year-old woman attended a police station by appointment today.
"They were arrested in connection with an allegation of serious sexual assault.
"They currently remain at the police station."
The incident is alleged to have taken place on May 5 in London.
A man in his sixties was arrested as part of the same inquiry in June, police sources said.
He was bailed until later this month.
The investigation follows an allegation of serious sexual assault in north London.
Earlier today the Hamiltons joined 500 other mourners at the funeral of penal reformer Lord Longford at Westminster Cathedral in central London.
Mrs Hamilton was in tears outside the cathedral after the service.
People who called the Hamiltons at their home heard the answer phone message: "Hello, not sure when we'll be back, so don't a leave message."
It directed callers to use Christine's mobile phone number.