Gunns Mill in the Forest of Dean is the best-preserved blast furnace of its type in Britain.

Historic England has awarded a grant of £163,812 to the Forest of Dean Buildings Preservation Trust to carry out urgent repairs at Gunns Mill furnace, one of Britain's most important industrial heritage sites.

The grant will fund the repair of the timber frame of the roof of the bridge house, which once protected charcoal and ore from the weather before being loaded into the furnace.

It is the only surviving bridge house for a furnace of this type dating from the late 17th century. The Trust plans to make this part of the building a usable space in the future.

The bridge house roof repairs were carefully planned in late 2023 with advice from architects and structural engineers.

This will be the third major repair project at Gunns Mill since 2020, when the Trust successfully completed repairs to the mill waterwheel pit. This was followed by urgent structural works to the north-east wall in 2022. Historic England provided grant funding and technical support for both projects.

Kate Biggs, of the Forest of Dean Buildings Preservation Trust, said: "The architects and engineers have prepared a solution and we are fundraising for the next steps to be undertaken. This is major progress in the journey of this building and would mean that we could remove some of the scaffolding after over 20 years!

"For many years the scale of the project and the masonry repairs required meant that this point seemed a very long way off. It now feels that goal is achievable for our small Trust."

Rebecca Barrett, South West regional director at Historic England, said: "The repair works to this rare 17th century bridge house have been carefully planned to take into account its fragility and structural complexity. It will be great to see work getting underway as a first step towards the building being used again in the future."

Gunns Mill is considered to be the best-preserved charcoal blast furnace in Britain. It dates from around 1682 when the Forest of Dean was one of the most important centres for iron production in the country, as it had been since the Roman period. It was converted to a papermill in 1743 but had fallen out of use by the 20th century.

The surviving lower tier of the building is a blast furnace that was built in 1625 on the site of earlier fulling and corn mills. Fulling, also known as felting, was a process involved in the production of woolen cloth. That furnace was destroyed in the Civil War and was rebuilt by 1682, evidenced by cast iron lintels with dates of 1682 and 1683. It continued as a blast furnace until 1738.

Local business owner Joseph Lloyd (who died in 1761) gave Gunns Mill a new use in 1741 by converting the building to a paper mill. The upper tier timber-framed building on the south side is thought to date from this phase.

By the late 19th century the mill was sold into a farming estate and used as a cow shed.

William Parker bought Gunns Mill in 1994 to prevent its conversion into a house. It was added to Historic England's Heritage at Risk register in 1998 and in 2000 it was given a protective scaffold which remains in place today. In 2013 William Parker donated the mill to the Forest of Dean Buildings Preservation Trust.

Gunns Mill is protected as a scheduled monument and a Grade II* listed building.

Mark Harper, MP for the Forest of Dean, said: "I am pleased to hear that the Forest of Dean Buildings Preservation Trust has received a further £163,812 of urgent investment to repair the timber roof structure of Gunns Mill Furnace.

"We must do all we can to ensure the survival of this important historical site, so that it may educate future generations on the Forest of Dean's rich industrial heritage."