The East London Line extension has government support and is ready to start. So why the delay, asks Andrew Bolton.
The East London Line is the Cinderella of London's Tube system.
It runs from Whitechapel, north of the Thames, to termini south of the river at New Cross and Surrey Quays, interchanging with the Underground's Metropolitan and District Lines at Whitechapel and with the Docklands Light Railway at Shadwell.
But the East London Line functions as a local Tube line rather than a strategic rail link.
The Strategic Rail Authority (SRA) and the mayor's transport executive Transport for London (TfL) want to change this by extending the line down to mainline rail hub Clapham Junction and rapidly developing West Croydon in south London.
They also want to take it up to the increasingly important north London transport nexus at Highbury and Islington.
The extensions are vital to provide direct north-south links through east London, where at present passengers are forced to cobble together a journey involving several changes between underground and main line trains.
The extensions will also help relieve congestion on other Tube lines that are groaning under the weight of too many passengers.
They will provide efficient commuter links from the suburbs to the City, and link east London's characterful but run-down Whitechapel and Shoreditch more effectively with the rest of the capital, spurring regeneration.
They are transport projects London badly needs.
So strong is the case for the £750M worth of extension and upgrade work that public sector supporters were ready to invite bids just before Christmas.
Like so many large transport schemes, however, the East London Line extensions have fallen foul of last minute doubts about costs and procurement methods. Fears are mounting that the scheme will be axed by the Treasury in this summer's Comprehensive Spending Review.
And there is the depressing prospect that, because the scheme is to be taken over by Network Rail once construction is complete, it is going to become bogged down in transport secretary Alistair Darling's ongoing rail industry review.
This would be a travesty.
TfL and the SRA have worked hard together to develop a robust procurement method using private finance for construction. The project would then be effectively sold to Network Rail on completion.
It has already jumped through numerous hoops including a 12 month planning dispute. Last summer the project finally won planning permission and also secured the endorsement of the Department for Transport.
It has been ready to go out to tender since the end of November.
If that were not enough, the project is named as a key component in London's bid to host the Olympic Games: It will provide one of the most direct routes for spectators travelling from the north and south to the east London Olympic centre.
The case for the East London Line extensions was developed as a result of its inclusion in the Department for Transport's 10 year transport plan, so presumably the government accepts it.
But continued indecision could seriously undermine the project's chances of being completed by the end of the decade, not least because hard won planning permissions for parts of the project will lapse later this year, resulting in further delays while they are renewed.
This project could start now.
If anything can signal that the government understands the importance of transport to the economy and has the guts to make the big decisions, then the East London Line is a first, easy win.