Two women, including a serving police officer, have been arrested as part of Scotland Yard's investigation into the so-called 'plebgate' affair involving former Tory chief whip Andrew Mitchell.
A 37-year-old police constable from the Diplomatic Protection Group, which is tasked with protecting diplomatic and government officials, was arrested at her place of work on suspicion of misconduct in a public office, the Metropolitan Police said.
A 46-year-old woman was also arrested at her place of work on suspicion of assisting the commission of an offence of misconduct in a public office.
The women have been taken to separate police stations - one in London, one outside of London - where they remain in custody.
The police officer arrested is one of the four officers previously issued with a Regulation 15 notice, and has been on restricted duties.
Scotland Yard said it expects the officer to be suspended later on Wednesday.
The plebgate row ignited when Mr Mitchell was accused of a heated rant against officers as he left Downing Street on September 19.
Pressure intensified after The Daily Telegraph published a police log of the incident, which claimed he called officers ''plebs'' and swore at them repeatedly.
He insisted he did not use the words attributed to him, and later said he was the victim of a deliberate attempt to ''toxify'' the Tories and ruin his career.
An email from a civilian witness backing up the police account of events has also since been called into question.
Some 30 detectives have taken statements from all 800 officers in the Diplomatic Protection Group (DPG) as part of the inquiry, which has taken nine months and cost taxpayers more than £140,000.