.
The new fleet was introduced by the then London Mayor Johnson, in 2012.
He described the vehicle as a "stunning piece of automotive architecture" and it reportedly cost £354,000 per bus for the initial fleet of 600 and then £325,000 for an additional 200 in 2014.
During his mayoral campaign last year, Khan pledged that if he was elected he would look into holding off further purchases of the Routemaster bus in order to make savings to help pay for a four-year public transport fares freeze.
When contacted for a comment, a spokesman for Khan said TfL is looking into investing in a new generation of buses that would focus more on improving air quality.
The Routemasters were reintroduced, seven years after the original was withdrawn and replaced by easy access low-floor buses was was celebrated by many as it it was a move to rid tthe capital of Ken Livingstone's unpopular "bendy" buses.
The fleet has suffered some glitches.
In October, it was reported that one of the vehicles burst into flames in the centre of London.
TFL tweeted a picture of the new bus next to a bus stop this morning, with large orange flames inside it clearly reflected in the glass.
The tweet simply said that Broadgate, between Threadneedle Street and Wormwood Street is closed due to a "vehicle fire" and did not offer any information on whether there were people in the number 22 bus or how it had started.
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