A 37-year-old police constable in the diplomatic protection group has been arrested on suspicion of misconduct in public office over the Andrew Mitchell "Plebgate" affair, Scotland Yard has said.
A 46-year-old woman has also been arrested on suspicion of assisting the commission of an offence of misconduct in a public office.
The arrests were made under Operation Alice, the investigation into whether officers lied about a dispute which led to Mr Mitchell being forced to quit the Cabinet.
They have been taken to separate police stations where they remain in custody.
The Independent Police Complaints Commission, who continue to supervise the investigation, has been informed.