The black, 40ft diameter concrete structure sits on land that used to be part of RAF Langham near the North Norfolk coast. Built in 1942 it was used to train anti-aircraft gunners using what was then state-of-the-art film technology to simulate approaching aircraft.

Originally in the ownership of Bernard Matthews Ltd, it was donated by the company to the North Norfolk Historic Buildings Trust together with about one-third of an acre of land.

Around 40 such domes were built around Britain but the one at Langham is one of only six known to survive and the only one that is accessible to the public. Already in a deteriorating condition, the structure, which has been listed as a scheduled ancient monument, will now be saved and restored by the North Norfolk Historic Buildings Trust, working with local volunteers who formed the Friends of Langham Dome three years ago.

When in use for training, pictures of moving aircraft were projected onto the dome’s interior with a beam of light projected from a mocked up anti-aircraft gun enabling the trainer to assess whether gunners hit their ‘targets’.

Innovative engineering techniques were used in its construction, but it has suffered from water penetration and some earlier inadequate repairs. The building will now be properly restored and equipped with reproduction technical equipment to show how it was used originally. Information to explain its history and its significance will be displayed, using modern projection and sound equipment, as well as displays about Second World War aircrews, aircraft and squadrons that served at the former RAF base.

The HLF grant will be complimented by £199,000 awarded by English Heritage, in addition to other, smaller sums from a range of local charities. A programme and volunteer co-ordinator  will help recruit more local volunteers and organise a range of activities involving the dome. These will include regular open days and work with local schools.

Robyn Llewellyn, Head of Heritage Lottery Fund East of England, said: "This is an intriguing structure whose fascinating secrets can now be revealed, understood and appreciated thanks to a project that will not only conserve it for future generations but also harness the enthusiasm of local volunteers of all ages."

For the North Norfolk Historic Buildings Trust Malcolm Crowder, Surveyor and Secretary to the Trust, said: "We are delighted that with the remarkable support we have from the local community and the financial resources brought to this project by our funders we are now able to restore and conserve this important structure and ensure its sustainable long term future."

Patrick Allen, Chairman of Friends of Langham Dome, said: "This is great news. A great deal of work has gone into getting to this stage. We are very grateful to HLF, as well as English Heritage and the other contributors, who have now shown faith in what we believe we can deliver. Langham was at the forefront of both defence and attack during the Second World War. Many of those that served here, came from across the globe, sadly many, never to return home, having made the ultimate sacrifice. The dome will now be able to tell their story and educate future generations of what happened at Langham."

Further information

Heritage Lottery Fund: Vicky Wilford, Communications Manager on 020 7591 6046 / 07973 401 937, email: vickyw@hlf.org.uk.

North Norfolk Historic Buildings Trust: Malcolm D Crowder OBE FRICS IHBC, Surveyor and Secretary to the Trust, 01603 622 938, e-mail: malcolm.crowder@btconnect.com.

Friends of Langham Dome (FoLD): Patrick Allen, Chairman of FoLD, 01328 830 348, email: patallen@lineone.net or visit the Friends of Langham Dome website.