Mr Hardy is leading opposition to plans which would see a 213ft incinerator built at the site of the Battle at Shrewsbury, which took place on July 21 1403 and reputedly saw the deaths of as many as 6,000 men in just three hours.
English Heritage initially opposed the scheme before switching to support the development and Mr Hardy has targeted the organisation with “an absolutely blistering” attack.
The 85-year-old actor – who plays Cornelius Fudge, the Minister of Magic, in the Harry Potter films – is a member of English Heritage’s own panel which advises on how to preserve battlefields. However, he has threatened to resign if the organisation continues to approve the scheme.
“As long as they stick to their renegment, I remain opposed to them,” he said. “I am doing whatever I can to stop the development. I have tried to make lots of noise about this blasted chimney.”
Mr Hardy is a world authority on medieval warfare and, in particular, the longbow, which for the first time in English history, was unleashed by two opposing sides at Shrewsbury, accounting for the high death toll.
He has been lobbying Simon Thurley, English Heritage’s chief executive, to reverse its policy again. In a letter threatening to resign he accused the organisation of “abrogating” its responsibilities in making the “wrong decision”.
Mr Hardy, who also starred in the long-running BBC series All Creatures Great and Small, added: “It is my business to defend the battlefield. It is where thousands of people out of divided but strong loyalties or compulsion, came together to test their arguments to the death.
“These are sacred burial places. We should honour those fields. The date of the battle doesn’t make any difference.”
The proposed incinerator is to be built by the waste company Veolia on the southern fringe of the battlefield, just to the north of the town, on land across which King Henry IV’s forces successfully attacked a rebel army led by Henry “Hotspur” Percy.
Opponents of the plans – which include the Battlefield Trust and a nearby visitor centre dedicated to the clash – say it would ruin views of the battlefield, which is otherwise largely undeveloped farmland.
Mr Hardy added: It is still possible to walk round the site and say ‘here stood …’, ‘here charged …’, ‘here resisted …’, ‘here fled …’ and so forth. You can clearly correlate between now and then.
“Part of the English Heritage mandate is to look not only to the approved site of the battle but also the environs and this new chimney would stand right between the visitor centre and observation points and views of the spires of Shrewsbury and the Welsh hills beyond. There are no really good reasons for it. The arguments for it are specious.”
The battle, which is described by William Shakespeare in Henry IV Part One, marked the end of a rebellion led by Hotspur, a powerful northern noble, against Henry IV, who had seized the throne four years earlier.
Hotspur’s family had initially supported the king but had fallen out and now supported a different claimant to the throne.
It is regarded as a preliminary chapter to the War of the Roses, the dynastic struggles which erupted later in the fifteenth century.
It was also the first battle in England in which both sides used the deadly and revolutionary longbow, which was employed by Henry V – Henry IV’s son, who was also present at the battle – to devastating effect against the French just 12 years later at Agincourt.
Hotspur – so-called because of his impulsive nature and whose name was taken up by Tottenham Hotspur FC centuries later – was killed in the battle, apparently after being struck in the face by an arrow while raising his visor to get some air. His body was buried after the battle, but later exhumed after rumours circulated that he was still alive. It was first displayed in Shrewsbury but later cut into four quarters and sent to different parts of the country. The king’s 16-year-old son – the future Henry V – was also struck in the face by an arrow which was only removed after the end of the fighting.
Veolia, the local council’s waste contractor, claims its proposed £60 million burner – which has already been approved by the Environment Agency – could generate enough power to supply 10,000 homes, as well as reducing the amount of waste going to landfill.
However, opponents have also voiced concerns about health risks for families living nearby.
Shropshire Council, which still owns the site, voted against the plans after members felt an incinerator next to the historically significant site was visually inappropriate.
But Veolia have appealed the decision to the planning inspectorate, which will hold a public inquiry in September. A spokesman for the company said: “The proposed site is on an industrial estate which is an existing employment area.
A detailed environmental impact assessment was provided as part of our planning application which was recommended for approval by Shropshire Council’s planning department.”
A spokesman for English Heritage said: “This is a finely balanced case. English Heritage accepts that the plant will affect the setting of the registered battlefield, but it is also true that the archaeology and understanding of the battlefield itself is not threatened.”
Special thanks to the Richard III Foundation for this article.