The central witness and victim in the trial of former Scotland Yard commander Ali Dizaei is under investigation for rape.
Waad al-Baghdadi, 25, was arrested last year by detectives probing an alleged sexual assault at a home in central London.
The freelance internet developer was questioned on suspicion of rape after a woman came forward to police. It is understood the alleged attack was a “historic” incident said to have taken place some time before.
The suspect was rearrested in Bayswater, west London, nine days ago on suspicion of breaching his bail conditions. He was released with no further action.
The investigation comes as Dizaei, 48, prepares to challenge his conviction for corruption in the High Court.
His legal team, led by Michael Mansfield QC, believe there is fresh evidence that shows the case against him is fundamentally flawed, and they want judges to examine claims that Mr al-Baghdadi used a false name and nationality when he appeared in court under oath.
Dizaei was jailed for four years in February last year after a jury found he attacked Mr al-Baghdadi outside a Kensington restaurant in a row over money.
The Iranian-born officer arrested the younger man and falsely claimed he assaulted him with a mouthpiece from a hookah pipe.
Details of the appeal are expected to be laid bare during a three-day hearing at the High Court in late March. No date has been set.
Neither Mr al-Baghdadi or Dizaei’s solicitor could be reached for comment.