The police officer at the centre of the "plebgate" row is seeking damages from former Chief Whip Andrew Mitchell of up to £200,000.
PC Toby Rowland is suing Mr Mitchell for suggesting the officer was not telling the truth about the dispute at the gates of Downing Street in 2012.
Mr Mitchell was accused of swearing at police and calling them 'plebs'.
The Conservative MP denies the allegations but resigned as chief whip in the wake of the controversy.
High Court documents show that lawyers for PC Rowland justify the claim on the grounds that his reputation has been damaged by Mr Mitchell's remarks and he suffered "great distress, humiliation and upset".
Boris Johnson said the police inquiry, which has lasted for more than a year, had taken a long time because new evidence emerged.
This is something that has been going on for an unconscionably long time. The difficulty seems to be - and obviously this is something about which I have asked the police, it's difficult for them to tell me too much and they have to be very guarded in what they can say because the inquiries are still going on - the trouble seems to be... that new testimony keeps emerging.
Boris Johnson says he believes one of the key officers involved in the so-called 'plebgate' row is receiving psychiatric care. Mr Johnson was speaking during a radio phone-in on LBC about the time it was taking to investigate the incident which led to the resignation of chief whip Andrew Mitchell.
The listing for the bike describes the item for sale as:
"A sturdy bike with blue frame, this men's Reflex Westminster has been a regular commuter to and from the House of Commons over the years with numerous journeys to the Department for International Development & Number 10 Downing Street.
Complete with front basket, lights, horn, gears, pannier rack and mud guards, this hard working two-wheeler, still in perfect working order, is now looking for a good home out of the limelight for its retirement years.
This is a seven year old Hybrid bike offering stability, comfort and ease of use, making it perfect for new cyclists, casual riders and especially urban commuters."
The bike of former chief whip Andrew Mitchell, which was at the centre of the "plebgate" row, is now for sale on eBay.
Mr Mitchell was riding the seven-year-old bike when police officers refused to let him leave Downing Street via the main gate last September. It was claimed at the time that Mr Mitchell swore at the officers and called them "plebs".
Mr Mitchell denies the allegation and was forced to resign after a series of damaging headlines. He has now put his "hard-working" Reflux Westminster for sale on eBay, wishing to give it a "good home out of the limelight".
All the proceeds from the sale will go to the charity Nyumbani UK, which helps HIV and AIDS affected children in Kenya.
The 18 speed bike with a basket has so far received 18 bids totalling more than £2000.
Andrew Mitchell, who has made a former complaint against Scotland Yard over the alleged leaking of its “Plebgate” report, has strongly criticised the Met’s handling of the situation.
In a letter to IPCC deputy chairman Deborah Glass, he wrote:
We are deeply dismayed that the Metropolitan Police appear to have leaked part of their Report prepared for the Crown Prosecution Service (CPS) to certain members of the Press and spun it to the advantage of the Police officers involved.
This was an Enquiry into a dishonest and illicit attempt to blacken my name and destroy my career. It would appear that this police enquiry continues precisely that process.