The government's highways agency says it had no alternative but to fill in a historic bridge, as anger mounts before it comes before a planning meeting.

National Highways blocked off the former railway bridge at Congham, near King's Lynn, in 2021, claiming it was essential safety work.

But the move sparked a furious response from heritage campaigners, who labelled it "vandalism", while West Norfolk Council has ordered the roads agency to apply for retrospective planning permission.

The bridge, on St Andrew's Lane, is expected to be discussed by the council's planning committee when it meets on October 2.

Eastern Daily Press: The bridge pictured before it was filled inThe bridge pictured before it was filled in (Image: Richard Humphrey)

National Highways has now set out why it carried out the work, which cost almost £127,000.

In a briefing to councillors, it says Norfolk County Council had recommended the bridge’s capacity be reduced from 44 tonnes to a 7.5-tonne weight limit in 2003, but this was never applied.

Urgent repairs were carried out in 2009. But National Highways said the structure continued to show movement and deterioration.

It adds: "The bridge’s poor condition, alongside its capacity issues required National Highways to act.

Eastern Daily Press: The bridge pictured before the Lynn - Fakenham line was closed in 1959The bridge pictured before the Lynn - Fakenham line was closed in 1959 (Image: M&GN Trust)

"The decision to infill was made to prevent an emergency arising, not in response to an existing emergency.

"It provides an important transport route for farmers and is used by modern agricultural vehicles which can weigh up to 30 tonnes."

The bridge was one of just six constructed in the 1920s by William Marriott, engineer of the Midland and Great Northern Railway.

But National Highways says it is not a designated heritage site and is not protected.

It says the bridge is not currently included in any proposed walking or cycling routes.

But it adds: "If any feasible future use is identified, National Highways have a commitment to fund the removal of infill material."

Earlier this year, Norfolk County Council said the former King's Lynn to Fakenham line, on which the bridge stands, could be used as a route for walkers and cyclists. 

More than 350 people have objected to the infilling on the council's planning portal.