They have sprayed graffiti on to the walls of the medieval Grade One listed building and in some cases even gouged out parts of the structure itself.

Community archaeologist Becky Wilcox, of Heritage Lincolnshire, said it was a sad fate for a landmark six centuries old, once home to members of the aristocracy.

Heritage Lincolnshire has plans to re-roof the building and possibly open it to the public at limited times, but Becky said these ideas would probably never come to fruition if the vadalism continued.

In this case, the public would never get the chance to see, first hand, the interior of a tower built before events such as the settling of the first American colonies had even been thought of.

Liz Bates, heritage development officer, said: "Standing at the foot of the tower, you can imagine
the awe the people of Boston felt as they approached the building in the 15th century.

"It was built as a display of the wealth and prominence of the owner and would have eclipsed all of the other small timber-framed buildings in the town."

She said it was important for people to realise the value of the tower as a major landmark. Because it is built of red brick, many people probably have no idea about how old it is, she said.
Plans are in the pipeline to refurbish the gardens around the tower, making them more suitable for
outdoor events.

These will go ahead regardless of the problems being experienced, but if the vandalism continues, it is likely the tower will stay locked up for good.