A police officer accused of falsely claiming to have witnessed the Plebgate row today pleaded guilty at the Old Bailey
Pc Keith Wallis, 53, of West Drayton, west London, admitted misconduct in public office between September 19 and December 16 2012, by saying that he had witnessed the incident and arranging for his nephew to support the claim.
He was charged after he sent an email to Conservative deputy chief whip John Randall, who was his MP, wrongly claiming that he had seen what happened in Downing Street on September 19 last year.
A row erupted when then-chief whip Andrew Mitchell became involved in a heated confrontation with another police officer, Toby Rowland, after he was refused permission to cycle through the main gate.
Mr Mitchell admitted swearing but denied Pc Rowland's claim that he used the word ''pleb''.
Wallis is from the Metropolitan Police Diplomatic Protection Group.
Mr Justice Sweeney, sitting at the Old Bailey, adjourned the case for sentencing on February 6 pending pre-sentence reports.
He released Wallis on unconditional bail but warned him that 'all sentencing options remain open to the court'.
Mr Mitchell, the Tory MP for Sutton Coldfield, welcomed the guilty plea.
He said in a statement: "I am pleased that justice has been done in a criminal court today.
"It is very sad and worrying for all of us that a serving police officer should have behaved in this way. There remain many questions unanswered, in particular why Pc Wallis wrote this email and who else was involved in this process.
"I am looking forward to seeing justice done in the up to 10 other related disciplinary cases involving police officers so that I can focus all my energy on delivering for my constituents and help David Cameron win a Conservative majority at the 2015 Election."
Wallis, wearing a black suit and tie, stood in the dock for the brief hearing.
He spoke only to confirm his name and that he understood the charge before entering his guilty plea at his first appearance at Crown Court.
No details of the case were set out and the judge allowed time before sentencing to prepare a psychiatric report.
In a statement, Scotland Yard said Wallis will face a misconduct hearing at the conclusion of all legal proceedings, relating to " discreditable conduct, honesty and integrity, and/or improper disclosure of information".
Four other officers have a case to answer for gross misconduct and will be subject to a misconduct hearing in relation to improper disclosure of information, the force said, with the earliest time the hearings can be held said to be in March.
Met Commissioner, Sir Bernard Hogan-Howe apologised to Mr Mitchell for the lie told by an officer, and said: "This investigation has been a ruthless search for the truth as at the heart of this are extremely damaging allegations that officers have lied and falsified statements against a Cabinet Minister.
"The evidence against Pc Wallis was such that he has entered a guilty plea. To lie about witnessing something and provide a false account falls way below the standards that I and Pc Wallis's colleague expect of police officers.
"His actions have also negatively impacted upon public trust and confidence in the integrity of police officers.
"I would also like to apologise to Mr Mitchell that an MPS officer clearly lied about seeing him behaving in a certain manner. I will be writing to him offering to meet and apologise in person.
"I expect my officers to serve the public without fear or favour, where officers break the law they must expect to be held to account and answer for what they have done.
"As there are still a number of gross misconduct hearings I must take great care not to say or do anything that prejudices the outcome of those very important hearings as these officers have important questions to answer."
Scotland Yard said another two officers will be subject to local misconduct action relating to providing inaccurate statements or inappropriate comments and a further officer has been recommended for management action in relation to inappropriate comments. The processes are currently under way, its statement said.
The court heard that Wallis had offered his resignation and admitted the offence in police interview before pleading guilty at the first opportunity in court.
Last month the Police Federation confirmed that the officer at the centre of the row was to sue Mr Mitchell.
Pc Toby Rowland issued a letter of claim for libel against Mr Mitchell relating to the issue in the wake of their differing accounts of the heated confrontation in Downing Street.
Prosecutors have found there was insufficient evidence to charge Pc Rowland with any criminal offence after the row, and Scotland Yard has said he will not face disciplinary action.
Mr Mitchell previously said he hoped the officer would give evidence on oath as part of the libel proceedings against the Sun newspaper. But Mr Rowland said he stood by his account of what was said.