Recent talk of a new railway line across London has tended to centre a single scheme - Crossrail. But for 16 years there has been another in the pipeline, now gaining in popularity fast. That scheme is Thameslink 2000.
There are three big reasons for the growing popularity of the north-south Thameslink over the east-west Crossrail. The most conspicuous could actually be described as 7bn reasons, as this is the cost difference between the £3bn Thameslink and the £10bn Crossrail. The second reason is the big O - London's 2012 Olympics.
Network Rail has bold plans to deliver 50% of Thameslink's capacity increase by 2012.
Third, there is a gut feeling that the second public inquiry into the scheme, just concluded, has gone well.
'I would like to believe we are on the cusp of a new era for the programme, ' says Network Rail's programme director Andy Mitchell. 'There were no problems at the inquiry, the company is in a far more credible position than it was, the industry is building a reputation for delivery, and regional development plans are already assuming it is happening.' The scheme has been rebadged 'the Thameslink Programme', getting rid of any embarrassment at having far overshot the millennial year, and much now hinges on the next six to eight months. The inquiry inspector will produce his report, deputy prime minister John Prescott must then give planning approval and transport secretary Alistair Darling must persuade chancellor Gordon Brown to cough up the £3bn.
This is no mean set of hurdles, but there is a big incentive: By 2012 Thameslink will be able to provide an extra 10,000 peak hour seats on trains into St Pancras, the central London transport hub for visitors heading to the Olympic Park. The full scheme will provide 20,000 extra seats in total, but this will not be attempted before 2012 since it will be competing for resources with Olympic construction works.
'Most people believe Thameslink is a right and sensible scheme, ' says programme director Andy Mitchell. 'But planning in such a complex area makes it a daunting prospect, ' he adds. By far the most of the £3bn capital spend is in an 8km area running from Farringdon to 3km south of London Bridge.
This work will have a direct effect on commuters as far afield as King's Lynn in Norfolk and Brighton on the East Sussex coast.
'Thameslink is about increasing capacity of a key north-south corridor. It's about getting people from north to south London and getting people from the south of London to London Bridge, King's Cross and St Pancras, ' says Mitchell.
'It is the capacity of that core that this is all about, ' he says.
Capacity will increase in three ways - longer trains, more frequent services and more on passenger space on the trains.
The plan is to extend eight car trains to 12 cars which means lengthening platforms at King's Cross, Blackfriars, Farringdon and London Bridge. At King's Cross this will be achieved by fitting out a new underground station box already built as part of the Channel Tunnel Rail Link terminus works at St Pancras (NCE 16 September 2004).
The station extension at London Bridge will be achieved through a £60M revamp which already has planning permission; at Blackfriars it will involve widening Blackfriars Bridge so that platforms can run from the station on the north bank of the Thames to the south bank, where a new station entrance will be added.
Around 50 further stations outside the central area were originally earmarked to be upgraded, but this is under review following the removal of slam door trains from the network - doors can now be programmed to open only where there is a platform.
More frequent services - up from seven peak time trains per hour to 24 between Blackfriars and Farringdon - will be achieved by relieving bottlenecks around London Bridge through the construction of a new twin track viaduct over the historic Borough Market. This will double the number of tracks into London Bridge to four. A new 'dive-under' grade-separated junction will relieve congestion at Bermondsey.
With the inquiry finishing this week, Network Rail is working on the assumption of a 'best case' outcome - a summer planning approval with a concurrent decision on funding.
With this in mind it is to consult industry in the New Year on what will be the most efficient way of contracting the works.
Network Rail plans to be very much 'hands on' and is leaning towards taking a programme manager role.
'We are keen to take a central role in delivery, ' says Mitchell. 'There are certain risks associated with this sort of project that only we can control.
The impact of getting some of this stuff wrong is massive, so getting an external party to manage these risks is not attractive.' Network Rail will also have a significant design role. 'System design will be done by us and only us. It's our bread and butter design work, ' he says, adding that Network Rail is also likely to want involvement in construction.
'There are some subcontractors out there that we should have direct relationships with.'