A medieval re-enactment has ended in real-world horror after a staged sword fight turned tragically authentic in front of stunned spectators — including children — at a historic English castle.

A 37-year-old man from Horsham remains in critical condition after being stabbed in the face during a mock battle at Bodiam Castle in East Sussex on Sunday.

Sussex Police said the sword pierced the man’s visor during the fight, which was part of a living-history demonstration.

Know the news with the 7NEWS app: Download today

Clad in full body armour, the man was rushed to the hospital with a severe head injury. His opponent, a 36-year-old also from Horsham, is assisting police with their investigation.

“We are treating the incident as an accident, and we are offering support to his family,” Detective Inspector Barry Chandler said.

“His opponent, a 36-year-old man also from Horsham, and the organisers are helping us with our inquiries.”

The display had drawn a large crowd to the 14th-century moated castle, which regularly hosts medieval displays and educational events. But what began as pageantry quickly turned into panic.

“It had been a really thrilling fight reenactment, and then suddenly it went catastrophically wrong,” one witness told the Daily Mail.

“It was clear the man was very seriously injured, and people were very shocked. Some kids were in tears. It was quite upsetting for everyone who was there.”

Built by a former knight during the Hundred Years’ War and now operated by the National Trust, Bodiam Castle is a popular family destination.

The Sunday event was meant to bring history to life — instead, it left attendees shaken.

Police have asked anyone at the event who may have taken photos or videos to come forward.

“We know that the re-enactment had drawn a large crowd and understand that anyone who witnessed the scene could have found this distressing,” Mr Chandler said.

“We are appealing to anyone who has photographs or videos of the interaction that led to the injury to contact us so we can gain a clear understanding of what happened.”