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.