A police constable has been sacked over leaks to the press linked to the Plebgate row, Scotland Yard said.
Gillian Weatherley was found to have breached standards of professional behaviour in relation to honesty and integrity; orders and instructions; confidentiality; discreditable conduct and challenging and reporting improper conduct in a three-day misconduct hearing.
She was on duty in Downing Street on the day of the confrontation between then-chief whip Andrew Mitchell and fellow constable Toby Rowland in September 2012.
The next day, Weatherley sent a photograph of an email that Rowland had sent to his bosses about the row to another officer, James Glanville. He was later sacked for leaking the information to the Sun newspaper.
Weatherley was found guilty of gross misconduct after the hearing before a panel which included an independent representative, a Superintendent and Commander Julian Bennett.
As well as sending the photograph to Glanville, Scotland Yard said Weatherley went on to exchange 12 text messages with him in the days following the confrontation, all of which she later deleted.
The force said she had given " inaccurate and misleading" statements to officers investigating the aftermath of the row, and had been suspended from duty since her arrest in February last year. Prosecutors have already decided not to press charges.
Another two officers, also from the diplomatic protection group, are due to face gross misconduct proceedings in the coming weeks.
The next hearing will begin tomorrow, for another Pc accused of denying he had been in contact with Keith Wallis, a fellow officer who was jailed and sacked for sending his MP an email in which he pretended to have witnessed the Downing Street confrontation.
A third constable will face her gross misconduct hearing on May 20, where she will be accused of giving false statements to the police investigation into Plebgate.
It is claimed she knew about Wallis's email and her partner leaked information to the Sun. The hearings are taking place in private as dictated by statute, but Mr Mitchell was invited to attend and Scotland Yard said it would publicise details of the decisions made.
The only misconduct hearing the force has previously held in public is that of Pc Simon Harwood, who was sacked after the death of newspaper seller Ian Tomlinson, when it was ordered to do so by police watchdog the Independent Police Complaints Commission.
Mr Mitchell said: "Disciplinary hearings in the Metropolitan Police are held in private and therefore I am limited in what I can say - at this stage.
"What I can say today is that I felt the hearing was well-conducted.
"This gross misconduct hearing was in respect of police officer Gillian Weatherley, who first obstructed my exit from Downing Street on September 19 2012 in breach of clear instructions from the head of Downing Street security.
"I hope the transcript of the inquiry and its supporting evidence will be published in full in the interests of openness and accountability.
"This case has serious consequences for the Government, the police and every citizen in this country."