Just as all roads once led to Rome, rail lines between East Anglia and the rest of the country pass through Ely North.

The main north/south route, from King's Lynn to King's Cross, and the east/west route, from Norwich to Peterborough, meet at Queen Adelaide, a few miles north of Cromwell's city.

Here the lines split in three, branching off via a trio of level crossings. It might look a trainspotter's paradise but the bottleneck formed by this sprawling junction is the main obstacle standing between half-hourly trains between King's Lynn and London.

All trains, regardless of their destination, have to pass through a short stretch of single track between successive sets of points.

Dualling it would cost �25m – a relatively small sum in the scheme of things compared, say, to the �33bn cost of the proposed high-speed rail link between London, the Midlands and the North. There have been meetings and manifestos, summits and cost-benefit analyses.

As Norfolk MPs took their case to Westminster in the spring, led by South West Norfolk's Elizabeth Truss, the feedback was encouraging from the start. The numbers stack up when you look at the potential returns for the region.

For improvements at Ely North would not only improve services and bring a boost to the likes of King's Lynn and Downham Market, their rural hinterland and the tourism trade a little further up the coast.

With plans for an expansion in life sciences and other hi-tech industries around Norwich, the rail link between the fine city and Cambridge will become a vital link.

Ministers admit the figures are compelling. There has also been an admission that East Anglia has not always had its fair share of funding in the past.

But while �25m is a relatively modest sum in rail terms, the question remains who is going to pay for it.

There are two options. The government could agree to include the work in a forthcoming capital spending round.

Another option is to make the work a condition of the next franchise to operate trains on the Fen Line, after First Capital Connect's tenure ends in September 2013.

The new franchisee would borrow the money from Network Rail and pay it back over the seven-year duration of its franchise.

But while the cost would be spread, fare paying passengers might find themselves coughing up for it, unless the franchise ring-fences fares from the upgrade.

Work on the junction would be relatively straightforward, involving the doubling of a section of track east of Roswell Pits, behind the old Ely Beet Factory, now a rail freight centre. It would almost certainly be a case of weeks or at the outside months.

Earlier this week, Euro MPs agreed to spend �3.5m on curing another bottleneck at nearby Soham.

The money will pay for a passing loop, which will enable passenger services to overtake freight trains, speeding up journey times and allowing twice the number of container trains to run between Ipswich and Peterborough.

chris.bishop@archant.co.uk