Down in the hole: Ross Lydall and Mike Brown survey the expansion work at Bank station

London’s transport chief today revealed that Sadiq Khan was “devastated” when he revealed he was leaving TfL.

Mike Brown, who stands down as transport commissioner on May 8 after five years, said he was privileged to have worked for the Mayor but said it would be good for TfL to have “fresh thinking” at the top.

Asked how Mr Khan reacted when he handed in his resignation, Mr Brown said: “He was devastated, he really was. I told him it was nothing to do with him.”

Mr Brown, who started working for London Transport in 1989, is leaving to become chairman of the £4bn redevelopment of the Houses of Parliament.

Today, in an interview with the Evening Standard, he warned that parts of the Tube were at risk of “serial decline” unless the Government helped to fund major upgrades.

Mr Brown said that a £1.5billion new fleet of 94 trains due on the Piccadilly line from 2023 would not be able to run any faster or more regularly than at present because there was no money to upgrade the “knackered” signalling system.

Bank station: a new southbound tunnel for the Northern line is being dug

A £656m upgrade of Bank station would not deliver its full potential on the Northern line because trains would still get stuck in a bottleneck at Camden Town, he added.

Mr Brown pleaded with Prime Minister Boris Johnson to ensure that any “levelling up” of spending with the North did not mean a “levelling down” for the capital.

“There are huge parts of the transport network that are still at real risk of serial decline,” he told the Standard.

“We have the two oldest fleets of trains now in the UK. The Piccadilly line trains were introduced in 1973, but they’re not quite as old as the Bakerloo line trains that were introduced in 1972.

“We will have, with no exception, the oldest two fleets of trains in the land. It’s quite remarkable that they’re still running, but it’s not sustainable.”

Installing digital signalling on the Piccadilly line would increase capacity by 60 per cent, he said. The cost is estimated at £2.45 billion.

Mr Brown said weekday passenger numbers on the Underground had doubled from 2.5m to five million since 2000 but “not one km of extra track” had been built.

There are no new projects in the pipeline once Bank station and the extension of the Northern line to Battersea power station are completed.

Holborn station was also desperately in need of expansion to cope with more passengers but no cash was available, he said.

Mr Brown was today in Goole, where Siemens is building a factory where the walk-through, air conditioned Piccadilly line trains will be built. He said this was a great example of how investment in London benefited the rest of the country.

He said the new trains would increase capacity by 12 per cent as they were slightly longer. But a new digital signalling system akin to the Victoria and Northern lines would increase total extra capacity to 60 per cent.

But he said: “I have no certainty of capital funding to enable that to happen.

“They will go exactly the same speed as just now. We will not be able to run any more frequency. It’s very much like a Ferrari on a country road.”

TfL’s finances have been badly hit by the loss of a £700m annual Government operating subsidy and the two-and-a-half year delay in opening Crossrail.

TfL will be deprived of about £1.35billion in lost fares due to Crossrail not opening under central London until summer next year [2021], as opposed to December 2018.

This is in addition to the £640m cost of Mayor Khan’s four-year partial fares freeze, though Mr Brown says that keeping TfL fares down has encouraged more people to travel.

There has been a decline in bus journeys. Tube journeys have been less badly affected but have failed to hit targets. However, income from Underground fares continues to rise as a consequence of the annual increase in Travelcards.

The overall impact on TfL’s finances is that it is not due to break even until 2022/23, a year later than planned.

Bank station: new access to the DLR is being created

Asked about the Mayor’s environmental policies, Mr Brown said electric cars were “not 100 per cent brilliant” because they emitted PM particulates form their brakes and tyres and because of concerns whether the electricity was from renewable sources.

“Private cars and inner London don’t really work together,” he said. “What you don’t want is hugely congested streets that are being used in an inefficient way.

“Single occupancy cars are very inefficient compared to the number of people you can get on buses or to give the space to cycleways or decent walking provision.”

He said the central London ultra low emission zone had been more successful than hoped, with about 70 per cent compliance in terms of vehicles meeting the exhaust emissions rules.

He predicted the Ulez expansion to the suburbs in October 2021 would also be a success. “I’m with the Mayor 100 per cent on this,” he said. “I think not tackling London’s toxic air is not acceptable.”