A second man has been arrested in connection with the Andrew Mitchell « plebgate » investigation.
The 23-year-old, who is not a member of police staff, was held on Wednesday night and has been released on bail. This follows the arrest of a police officer on Saturday.
Mr Mitchell quit as chief whip after it was alleged he called Downing Street police « plebs », which he denies.
CCTV footage has cast doubt on the original police accounts of the row.
The man was arrested in north London at around 20:00 GMT on Wednesday « on suspicion of intentionally encouraging or assisting an offence of misconduct in a public office on or around last Friday ». His home was also searched.
BBC home affairs correspondent Danny Shaw said this had been « about the time police received fresh information about it [Plebgate] ».
Prime Minister David Cameron, speaking during a visit to Afghanistan, said a « full-scale police investigation », supervised by the Independent Police Complaints Commission, was needed.
« I think that’s very important. Let’s get to the truth, » he said.