VANDALS have toppled a wall at Burgh Castle's magnificent Roman Fort that has stood firm since the third century and witnessed immense changes.

Despite mounting regular patrols at the tranquil beauty spot, which has become a haven for anti-social behaviour over the summer key keeper, John Russell discovered the 'appalling' attack last week.

But Mr Russell, who lives nearby, said he did not suspect the rowdy youngsters who congregate there, leaving a trail of bottles and litter, but rather thought it was down to two or three teenagers messing about.

He said: 'My wife and I walked around the fort in the afternoon and it was lovely and sunny and there were families picnicking. 'I went out again at around 10pm to check there was no-one misbehaving, and I found part of the wall had been pushed over. I was appalled.'

Dr Peter Wade-Martins, director of Norfolk Archaeological Trust which owns the site, said the section was probably only two or three feet high but was in the right position, as it had been for centuries.

The fort, one of the best preserved in Britain, was part of a coastal defence system built to protect England from invasion in the third and fourth century.

At one point in the 11th century the Normans, under William the Conqueror, had made alterations which included breaching a wall and adding a wooden fort on the mound – causing the precarious looking tilt to one of the walls which is properly underpinned, despite appearances.

The vandalism happened on the best preserved of the three walls on the south side by the river, which offers stunning views across the water towards Halvergate, reckoned among Norfolk's best.

'It is just so sad that people do not seem to respect an ancient monument of that importance,' said Dr Wade-Martins.

The fort recently benefited from a �400,000 programme to improve visitor access and information while enhancing the setting with landscaping. The scheme included adding a car park and gates which have to be locked every night.

A decision on what to do next is awaited from English Heritage which, despite not owning the 90 acre site, is responsible for the legal protection of the walls.

In places the walls are reckoned to be up to eight feet wide. Over the years some of the flints have been robbed for souvenirs, although nothing on the scale of the recent attack has happened before.

It is estimated the section weighed at least a tonne and that the vandals had put themselves at considerable risk by their 'mindless' actions.

Mr Russell has been a key keeper since September and is a volunteer on the Lydia Eva herring drifter moored at South Quay.

'It's a beautiful spot,' he said. 'I treasure it and just want to look after it.'