Teenager walking on top of Sandsfoot Castle

The youngster was spotted balancing precariously at the summit, seemingly not worried about the 30ft drop below.

Her behaviour has been condemned by police and community leaders who want to stress how dangerous it is. Such thrill-seeking antics can end in tragedy, it is warned.

Anyone tempted to copy such behaviour is being urged not to and to think of the consequences.

This comes after a number of people were injured jumping off Durdle Door.

The girl at Sandsfoot, believed to be aged around 14, walked along the top of a narrow uneven wall, and it is understood she was egged on by a group of friends who watched from the ground.

It was all witnessed by a couple who had been enjoying a picnic in the castle grounds.

Doug Randle - a local amateur photographer - and his wife Maureen spoke to the girl about the dangers and said she was apologetic.

Mr Randle said: "We watched in disbelief.

"The girl was approximately 14 or 15 years old and in a group of four girls.

"She went up there twice and made it safely back down.

"The others had been encouraged to join in but seemed to think better of it.

"There were many families sitting around in the grounds but didn’t appear to see what was happening.

"My partner Maureen spoke to them afterwards, suggesting that what they were doing was risky. They were polite in response."

Sandsfoot Castle was built by Henry VIII to protect against invasion by France.

It is a scheduled historic monument and is looked after by the local authority assisted by the local Friends group.

The castle has sadly been targeted in the past by vandals and is a known hangout for local children who have been spotted climbing on the walls before.

The castle was renovated in 2012 thanks to lottery funding with particular attention to the top of the walls.

Local councillor Clare Sutton said of the girl's antics: “This is extremely irresponsible behaviour. Not only did she put herself at great risk, she also risked wasting the valuable time of emergency services had she fallen or needed to be rescued.

"There is also the risk that others might see this and think, 'That looks like a good idea'. It’s not. PLEASE don’t."

Neighbourhood Inspector Barry Gosling, of Weymouth and Portland police, said: “It should be nothing short of obvious that climbing onto the roof of any building is an incredibly dangerous thing to do.

“Sadly, while such antics may be seen as amusing or thrill-seeking, they can end in tragedy.

“I would urge this activity to stop before somebody is seriously injured or killed.”

'Parents and schools should be alerted to this'

Chairman of the Friends of Rodwell Trail and Sandsfoot Castle Gardens Paula Klaentschi said: "It will carry on unless a way to stop it is found. When the castle was fenced off it did nothing to prevent this situation; indeed it made policing even more difficult and dangerous. Opening it up with the renovations did not make the frequency any worse indeed the public monitoring did improve respect and appreciation.

"Perhaps the only thing one can do is alert parents and schools of this behaviour and remind them that this is our only Scheduled 1 Historic Monument in Weymouth and a major attraction. It is not a climbing playground. We all should cherish and respect it."

Weymouth Town Council is urging everyone using local open spaces to act responsibly. Take litter home, do not light fires or use disposable BBQs, and take care.

A spokesman said: "We all have a duty to protect our emergency services from unnecessary call outs. Sandsfoot Castle is a Scheduled Monument and listed Grade II. It should not be climbed on. This is very dangerous for people as well as the monument itself. Damage to the monument is an offence."