Despite the mayor acknowledging that "Piccadilly line service has not been good enough" with ongoing disruption caused "for thousands of people," the launch of the Night Tube will go ahead as planned.
It starts on the line - the fifth to get the all-night treatment - on Friday 16 December and will run all night on Fridays and Saturdays.
Around half of the Piccadilly line's fleet had been taken out of service for wheel repairs when problems started in November, but Transport for London (TfL) is confident there will be enough for the Night Tube.
It's bringing around 66 trains out by this evening and will need around 25 for the Night Tube services. The line needs 79 trains for full service at peak times.
Wet leaves and cold weather make the train tracks slippery, meaning the Piccadilly line wheels often lock when braking, damaging the wheels and the tracks. Newer trains on lines such as the Circle, Hammersmith and City and District lines have wheel slide protection; older trains on the Piccadilly line, which were built in 1973, do not.
The Rail, Maritime and Transport (RMT) union has called on the Night Tube launch to be delayed, saying the Tube problems could last until February. TfL though, has said it expects full service to be resumed in the next few weeks.
Speaking at Mayor's Question Time today, Sadiq Khan said "a full review of this year's events is being carried out" to look into TfL's preparations, response and the recovery process. He said "lessons must be learned to ensure this does not occur again".
"I've told TfL to fix this as a top priority and teams have been working around the clock to repair the damaged wheels that were causing the delays," Khan said. "All passengers that have been delayed have also received backdated refunds."
The mayor also took the chance to have a dig at his predecessor Boris Johnson, saying that under Johnson, "the vital Piccadilly line upgrade was delayed" which would've brought new trains to the line "and stopped this from happening".
Khan said there will be "no more delays" to the delivery of the Piccadilly upgrade, with resignalling work starting in 2020 and new trains arriving from 2023.
He has also dropped a hint that driverless trains will be brought in with the upgrade. "It would be unwise for us to buy stuff that isn't future-proofed," he said in response to a question over whether the trains will be capable of being driverless. "You would order the machinery that's fit for purpose going forward."
Where will the Night Tube services run on the Piccadilly?
There will be a train every 10 minutes between Cockfosters and Heathrow Terminal 5, excluding Terminal 4. Standard off-peak fares will be charged and Day Travelcards cover journeys made until 04.29 the next day.
The Night Tube is already running on the entire Victoria and Jubilee lines and most of the Central line, between Loughton/Hainault via Newbury Park, and Ealing Broadway and Northern line Charing Cross branch, excluding Mill Hill East.