De Valera’s former safe house (and cabinet nuclear bunker site) in Co Kildare for €1.6m

Few properties have had as many incarnations as Firmount House outside Clane in Co Kildare. Part of the house dates from the Georgian era but the bulk of this gothic pile is from the Victorian period; there is also a structure in the basement thought to date from the 13th century.

It was originally one of the residences of the Warburton family – who also owned Straffan House which is now the five-star hotel and golf resort known as the K Club. It subsequently became the family home to the Deasys until it operated as a military hospital during the first World War, followed by a run as a safe house for Irish politician and patriot Éamon de Valera.

It then operated as a sanatorium for tuberculosis patients until 1964, when it was purchased by the Department of Defence and used as a control centre for nuclear tracking during the cold war. Not only was it used for tracking – where "there were 60 telephones in the basement" according to the current owners, but the department of defence made the basement into a bunker, which was to be used by senior government officials in the event of a nuclear war.

Back then, the thought was that reinforced concrete would fully protect humans against the perils of a nuclear fallout, so when the owners Eilin O'Carroll and David Pansegrouw purchased the property in 2012 for €250,000 they needed a tractor to dig out the basement. At the time "there was a waterfall coming down the staircase" and by the time the contracts were signed "the walls had turned black" according to O'Carroll, an asset management consultant.

With missing floors and a huge damp problem, the main house needed to dry out at a specific humidity for two years before the couple could start the renovation. “We had no budget to do it either – and the banks would not give finance as it was so derelict, so while it dried out we began to renovate the Doctor’s House,” recalls O’Carroll. The Doctor’s House is a second property adjacent to Firmount itself and is about a century old, and the renovation of this four-bedroom, 350sq m (3,750sq ft) light-filled home featured on RTÉ’s Room to Improve.

After two years, addressing the challenges of Firmount and its seven acres of grounds began with the old servants’ quarters on the top floor of the three-storey over basement pile. The couple then used volunteers through the Wwoofer and HelpX websites, where workers aged between and 18 and 24 sign up to work for free in exchange for accommodation, food and drink. “They were a godsend and cleared three acres of the gardens while helping us to restore windows and build walls. It was also great for our kids as they were growing up in a really multinational family,” recalls O’Carroll.

During the renovation of the main house, curiosities such as a Geiger counter, hundreds of miniature glass bottles, helmets from the second World War and a rather unusual tube of cream from the 1940s, with instructions to put it under your nose in the case of a poisonous gas attack, were uncovered. O’Carroll says they have hidden them in the house so new owners will have the same fun finding little pieces of this most unusual property’s history scattered throughout its 1,207sq m (13,000sq ft).

The main property has been used as a wedding venue and film set for the past few years, while the family lived in the Doctor's House, and there is also a converted studio on site. Caught by the renovation bug, the couple and their two children are off to France to renovate an old chateau, and have placed their home and the seven-bedroom period house with a commercial kitchen and space to seat 110 people at dinner, on seven acres of gardens, on the market through Savills seeking €1.6 million.