A police officer has been arrested over the "plebgate" affair which cost former chief whip Andrew Mitchell his job, following what Scotland Yard calls "fresh information."
The 48-year-old police constable, from the diplomatic protection group, was held on suspicion of misconduct in a public office this morning as part of Operation Alice, the investigation into whether officers lied about a dispute which led to the Tory MP for Sutton Coldfield being forced to quit Cabinet.
As Mr Mitchell admits, he had an ill-tempered argument with police officers at the gates to Downing Street in September last year, when they wouldn't let him ride his bike through the main gate. The following day, The Sun reported that in an expletive-infested rant, he called the officers "plebs".
Such a furore was caused by the allegation that after a month of bad press, Mr Mitchell resigned.
He insists that he never used that word, and that he fell victim of a deliberate campaign to "toxify" the Conservatives and ruin his career.
The arrested policeman is one of four officers previously issued with a Regulation 15 notice, served following an alleged breach of standards of professional behaviour.
He has been on restricted duties and is expected to be suspended later today.
A 49-year-old woman - who is not a police officer - was arrested at a separate address on suspicion of assisting an offender.
The two were taken to separate police stations, one in London and another elsewhere, and remain in custody.
A Scotland Yard spokesman said: "On June 4, officers working on Operation Alice received fresh information regarding the investigation.
"As a result of this information and subsequent investigations, the Directorate of Professional Standards has arrested two people, a man and a woman, at two residential addresses, this morning."
The Independent Police Complaints Commission, which supervises the investigation, has been informed