There is even the possibility that they may have to be taken off the road if London Transport's financial crisis cannot be solved.
Sadiq Khan has been forced to defend plans to impose his biggest increase in council tax bills since becoming mayor.
This includes £20 a year for the next three years to help ease the financial crisis at Transport for London – though the first year’s money will be held in City Hall’s coffers and not spent for 12 months.
A thousand of the buses were introduced by Boris Johnson in his second term as mayor, at a cost of about £350m, as a replacement for conventional buses and the last of the classic 1960's AEC Routemaster double-deckers.
They are approaching their “mid-life refurbishment”, required about seven years into an expected 14-year lifespan, but TfL is struggling to find the estimated £31m needed to carry out the upgrades.
TfL‘s current Government bailout has been extended until February 4 but TfL commissioner Andy Byford said the organisation was assuming a “Domesday scenario” of moving to the “managed decline” of the public transport network due to uncertainty over long-term capital investment.
TfL also fears its hopes to electrifying the capital’s 9,000-vehicle bus fleet by 2034 will be delayed by three years to 2037 and it has already warned that 100 routes may have to be axed and frequencies reduced on 200 more, as part of an 18 per cent reduction in the bus network.
TfL has begun advertising contracts to refurbish the Boris buses, which were built by Wrightbus in Northern Ireland and unlike other buses are directly owned by TfL – meaning it has to meet the refurbishment costs.
This includes spending up to £5m on new driver’s seats and £1m on pre and post-refurbishment inspections.
A total of about 20 changes are due to be made to return the buses to “as new” condition. These include new passenger seat covers, a re-spray of the red exterior paint, upgrades to the fire suppression system, a “deep clean” of the interior and new customer signs.
Sadiq Khan refused to buy any more Boris buses on succeeding Mr Johnson as mayor in 2016. The vehicles attracted controversy, having initially been designed without opening windows – leading them to be dubbed the “Roastmaster” during the summer. They also had a poor record on emissions.
Mr Khan said bus manufacturers across the UK would suffer if TfL was unable to lead the move towards electric buses.
The design for the New Routemaster features three doors and two staircases to allow accessible boarding. The layout of the new bus allows it to be operated by one person, but when it was first introduced a second crew member was positioned at the rear entrance which was left open, just like on the original Routemaster. This allowed passengers to hop on and off when the bus was stationary in traffic.
Readers for the contactless Oyster card used for payment for transport in London are provided at each of the three boarding points. Other types of ticket must be presented to the driver. When a second member of staff was on board they did not take fares or check tickets and were just there to supervise the hopping on and off..
Eventually the cost of a second crew member became too much to justify and since then the buses have been operated with just one driver who supervisors boarding through the front entrance like a conventional modern bus, the middle and rear doors becoming exit-only.
The cost of each bus was £355,000 over the four-year procurement period. The last of the 1,000 New Routemasters was delivered in December 2017.
The bus is a hybrid diesel-electric driven by a battery-powered electric motor, charged by a diesel fuelled generator and recovering energy during braking by regenerative braking.
Below, some of the New Routemasters are running around in various advertising liveries, none of which seem to particularly suit the vehicle.