The Victorian marvel has attracted countless visitors to its cliff-top location at Trow Point, in South Shields.

But National Trust chiefs fear it is now slowly being destroyed by vandals scrawling over the monument, and leaving broken glass and litter behind.

The gun is a replica of a weapon which once stood on the concrete plinth during the late 1800s as part of a British Army experiment to find the best type of mounting for its breech-loading coastal defence guns.

The original gun was removed after the trial, about 1887.

National Trust property manager for The Leas and Souter Lighthouse, Nick Dolan, said: "What should be a beauty spot to be proud of is today a showcase of vandalism.

"It is a site used by young people. That would be fine, but the graffiti, rubbish and broken glass they leave from their drinking and activities is unacceptable.

"It shows a lack of respect for the area they live in, and for the National Trust.

"As owners, we have to tidy up after them and spend the charity's limited money and resources on repairing their damage.

"It is very frustrating, to say the least as it is not the first time it has been vandalised."

The National Trust is now working with South Tyneside Council to see what can be done to improve the site.

It is also calling on people who visit the site not to leave their litter behind.

Independent Coun for Horsley Hill, Gordon Finch, said: "What these vandals are doing is disgusting.

"It is a monument which has been put there to remind us of something which has happened in the past.

"It is disgraceful to think people are destroying what is a lovely spot on our coastline.

"I would appeal for anyone who sees someone causing any kind of damage at the site to report it to police, the National Trust or to me."