Campaigners have been accused of sharing "conspiracy theories" during the final day of a public inquiry to determine the fate of a historic railway bridge filled in with a thousand tonnes of concrete.
The comments were made during the closing remarks at a hearing to decide whether National Highways will have to remove the material it poured under the Congham crossing near King's Lynn.
The agency caused outrage among locals and heritage groups for the infill of the 1920s bridge and was told to reverse the work by West Norfolk Council (WNC).
A government inspector will now make a final judgment on the dispute after the public body appealed against the council's enforcement order.
It has held a public hearing, lasting several days, to hear evidence from both sides.
Tim Leader, speaking for the council, argued National Highways' actions were a "gross breach" of planning policies, arguing the body of evidence shows the council made the right decision.
However, Martin Carter, a barrister for National Highways attacked the evidence put forward by Graeme Bickerdike of the Heritage Railway Estate Group, who accused the agency of "destroying history".
He said Mr Bickerdike had been spreading "conspiracy theories" that National Highways tried to intentionally mislead authorities over the reason it filled it in with concrete - it claimed it was in a "very poor condition" and had become unsafe.
He also disputed several claims that formed the basis of the council's decision to refuse planning permission, arguing the crossing is not a significant heritage asset.
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He instead said it was of low historic and aesthetic value and questioned the bridge's ties with famed architect William Marriott, arguing it was built after his retirement - although his construction system played a pivotal role in its design.
But following the hearing, Mr Bickerdike said the evidence "spoke for itself".
"National Highways has misled the public, the council and the inspector time and time again. It is what they do when you criticise their unlawful infill schemes.
"There is no evidence to substantiate their claim the bridge was in a very poor condition."
In his final remarks, Mr Carter asked that National Highways lost the case, it should be given 24 months to remove the material, rather than just the 12 months granted by WNC.
Planning inspector Laura Renaudon will now consider her verdict before issuing her decision which is expected to be made public shortly after the General Election.
A PIECE OF RAILWAY HISTORY
Congham Bridge is one of just six which were built in the 1920s using Midland and Great Northern Railway engineer William Marriott's designs - featuring unique curved wingwalls.
The railway route connected South Lynn with Fakenham before continuing on to Great Yarmouth.
But in 1959, it was decided that the Lynn to Fakenham line should be closed.
The bridge had remained in use, carrying a quiet country road, St Andrews Lane, across the now-abandoned track.
But a century after it was opened, it had become corroded and began to develop fractures.
This led National Highways to fill it in with concrete.
However, heritage groups claim the structural issues were misrepresented and that it should have been repaired to preserve this piece of railway history.
Congham Bridge is the second railway crossing that National Highways has been ordered to restore and it is one of 51 bridges that have been infilled since 2013 at a cost of £8m.
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