Campaigners have warned about the uncertain fate facing a handful of former railway bridges in Norfolk, which could fall victim to a controversial project which would see them demolished or filled in with concrete.

National Highways (NH) has drawn up a list of dozens of disused structures across the country which it wants to knock down or infill, and some in Norfolk have already been lost.

A national outcry against the policy led to the scheme being halted earlier this year, but campaigners are concerned that many bridges, including some in the county, are still under threat.

The Heritage Railway Estate (HRE) Group, which is organising the defence of the structures, fear the programme - which NH say is designed to make the bridges safer - will resume.

"These are national assets and we need to derive the greatest possible benefit from them," said group member Graeme Bickerdike.

According to NH’s major works programme for the next five years, two bridges in Norfolk could see works carried out.

One is the Leeds Bridge at Themelthorpe, near Reepham, which lies on the so-called Themelthorpe Curve - once the sharpest curve on the country's rail network. It is currently undergoing “structural assessments”, with “maintenance options under development”, say NH.

Another is at Aldeby, on the former Great Yarmouth to Beccles line. The bridge has been infilled on one side, with further infilling on hold.

Two bridges in west Norfolk have already recently been lost. It was decided to infill one at Congham, on a former line which ran from King's Lynn to Fakenham, while another at Wiggenhall St Mary Magdalen, on a line from Lynn to Wisbech, was demolished earlier this year.

A bridge at Saxthorpe, near Reepham, on a line from Yarmouth to Melton Constable, was also threatened with infilling, but the decision has since been deferred, leaving its fate unclear.

The infilling policy has caused controversy across the country.

Campaigners say it can create ugly blights on the countryside and also threatens the work of many restoration groups who want to revive now defunct train lines.

One such group is the Melton Constable Trust (MCT), which hopes to create a Norfolk Orbital Railway from new and old rail lines.

It breathed a sigh of relief earlier this year when it was agreed that a Victorian roadbridge at Gateley, near Fakenham, would not be infilled.

The bridge passes over the former trackbed of a line which ran from Wells to Wymondham and would have proved crucial for the group’s plan.

The Orbital Railway would run from Holt to Dereham on existing lines via Sheringham, Norwich and Wymondham, and on a new stretch of track via Fakenham to create a loop.

The Gateley roadbridge was due to be infilled by NH but following talks with the county council and other groups, a fix was found.

“The county council has been enormously helpful on that one. They’ve gone to great lengths to suggest a solution that would save the scheme,” said MCT director David Bill.

“To make the bridge safer, they are suggesting narrowing the roadway over the bridge so that only cars [rather than lorries and larger vehicles] can go over it.”

If those physical restrictions prove effective, then NH will not infill the bridge.

In total, 68 former railway bridges across the country could be infilled or demolished.

What was the Themelthorpe Curve?

This bend of track was at one time the sharpest curve in the British Rail network and connected two separate lines.

The lines had been opened by rival companies before the post-war nationalisation of Britain’s railways.

The Midland and Great Northern line had originally joined Norwich with Melton Constable, in north Norfolk, while the Great Eastern Railway line crossed over it to link Wroxham with County School station, at North Elmham, between Dereham and Fakenham.

Opened in 1960, it was the last section of track built in Norfolk by British Rail, and only saw 25 years of use before its closure in 1985.

The curve was built to allow freight to travel from one side of Norwich to the other without having to journey up via Cromer - and it was so sharp that trains were limited to a speed of 10mph when traversing it.

The former trackbed of the curve now forms part of the Marriott’s Way footpath, and is home to the largest badger sett in Norfolk.