UNDERGROUND workers yesterday gave the thumbs-up to all-night Tube running in London, but there are doubts whether the service will start before Mayor Boris Johnson leaves office in May.

London Undergound operations director Steve Griffiths said the company could now focus on delivering the project “as quickly as possible.”

But a source close to negotiations said it was highly unlikely it would be rolled out before the capital’s mayoral election in May.

“Now the question is whether it will be introduced at all,” they said.

Members of rail union RMT voted by an 84 per cent margin to accept an offer from London Underground, which includes three years of above-inflation pay rises and a £500 lump sum for staff affected by the Night Tube. Bosses are also expected to start trialling a four-day flexible working week for train operators.

Drivers’ union Aslef is expected to endorse the deal next week, while Unite and TSSA have yet to ballot members on the offer.

The London mayor planned to start Friday and Saturday night running last September, but two crippling summer strikes by workers concerned about work-life balance forced him to call off the launch.

Yesterday RMT general secretary Mick Cash said: “I want to pay tribute to RMT’s members across London Underground who have stood rock solid throughout the long campaign of industrial pressure to secure a fair deal.

“Those members have now voted to accept the most recent offer from the company — an offer that was only made after the hard work by union reps in the negotiations, backed up by the loyalty, determination and militancy of the workforce.”