Urgent works to restore an area of overgrown and historic scrubland to its original glory will begin later this year.

Thetford Warren Lodge is one of only two surviving structures of its kind in the country, but, under the lease of Breckland Council, the surrounding landscape has become overrun with trees, bracken and heather.

Natural England has now said the 11 hectare site is in an 'unfavourable and declining condition' and an agreement with the council and the Brecks Partnership has been reached to restore the area to natural heathland.

Manager of the Brecks Partnership, Neil Featherstone said it could take up to eight years for the site to return to a 'favourable' condition. 'From a biodiversity point of view it should be open heath,' he said. 'At the moment there's a large cover of bracken and lots of trees there and the area is declining because no work has been done there for some time. In order to save the species for which the area is special we need to manage the land.'

A letter was sent by Natural England to the council in 2010, identifying its failure to meet its obligations to the Site of Special Scientific Interest (SSSI).

It said the council could face enforcement action if it did not meet its legal requirements to maintain the area, and offered a grant of �78,151 to complete the works. These will begin in early summer with the removal of bracken followed by the removal of trees in October.

Mr Featherstone added: 'I think the vast majority of people view removing trees as against conservation but in some cases it's actually what needs to be done. We want to put the warren lodge in it's warren context. If it's open land it will give some idea of what it would have once been.'

Thetford warren lodge is believed to have been built around 1400 and would have protected gamekeepers and hunting parties against armed poachers. Much later it was used by local warreners who harvested rabbits. The heathland would have been kept short by the nibbling of these animals and sheep. It is expected heathland plants will naturally re-cultivate once the work is complete.

Anne Mason, who has been researching warrens since 2000 when, as a member of Friends of Thetford Forest Park, she was asked to raise funds to restore a medieval warrener's lodge in Mildenhall Woods, added: 'A warren lodge was the highest point of a town and it would have sat very proud in its landscape and would have been surrounded by heathland. Thetford warren lodge is highly significant because there is only Thetford and Mildenhall left. There are no other buildings left in the world like these.'

Breckland Council was unable to comment.