• A long-awaited restoration of 'at risk' Acheson House has finally got under way, 15 years after its rescue plan was first unveiled Picture: Andrew Stuart
Acheson House, built by a Scottish secretary in the 17th century, is on the city's official "at risk" list, despite being rated one of the most important surviving buildings in the World Heritage Site.
The city council has started the first phase of work that will eventually see it become part of a new-look Museum of Edinburgh, although it is thought it could take several years to fully restore it to its former glory.
Edinburgh World Heritage and Historic Scotland are expected to be approached to help bring the A-listed building back into public use.
The work to repair and restore its slate roof is the first major revamp of Acheson House since it came into council ownership in the early 1990s.
The run-down building, hidden down a close opposite the Royal Mile's Canongate Kirk, fell into decline in the 18th and 19th centuries, becoming a brothel and then slum accommodation.
However, it was rescued in the 1930s by the Marquis of Bute, who donated it to the nearby church, and the building was run as a craft centre from 1956 to 1992.
A succession of plans to bring it back into public use have come to nothing since then and it has been on the Scottish Civic Trust's official "at risk" register for several years.
Terry Levinthal, director of the Scottish Civic Trust, said: "This work is long overdue. There has a real dearth of activity over Acheson House, even though it is of such significance. It's probably one of the oldest buildings anywhere in the country on our buildings at risk register."
A spokeswoman for the council said work was expected to be carried out in phases and that funding was still being sought for its longer-term future as part of the museums hub.
Edinburgh culture leader Deidre Brock said: "This would enable us to create a world-class museum devoted to telling the fascinating story of Scotland's capital city."
Adam Wilkinson, director of Edinburgh World Heritage, said: "Acheson House is one of the most significant buildings in the Old Town, but its location as part of a complex of historic buildings in Bakehouse Close is also of note. It is one of the few closes that was never 'improved' and so still retains a real sense of how the Old Town would have looked and felt hundreds of years ago."
The house, which is in Bakehouse Close, is named after Archibald Acheson, who served as Secretary of State for Scotland under Charles I.
A bid to breathe new life into Acheson House was revealed in 1995 by the then district council, which proposed linking it with a 16th century former mansion, Huntly House, which is home to a museum about the city.
Detailed plans to showcase the city's hidden gems were unveiled five years later but have stalled because of funding problems.
Heritage groups have warned the council Acheson House has been "deteriorating rapidly" and large quantities of asbestos were discovered there eight years ago.