A Victorian fort, which acted as an anti-aircraft battery in World War Two and has now been converted into a home, is on the market for £1.5 million.
Set within 50 acres of land, Fort Borstal features an extensive network of Napoleonic underground tunnels and a two-bedroom house.
The five-sided citadel was built in 1875 by convict labour in a bid to hold the high ground southwest of Rochester, Kent.
It was one of four forts that ringed nearby Chatham – home to the historic Royal Navy dockyard.
It became the base of an anti-aircraft battery in World War Two, shooting down German aircraft targeting the military docks.
After the conflict, the site was transformed into a pig farm and was used as a store for the nearby Young Offenders Institution.
It was sold in 1991 to a company hoping to turn it into a museum but the project was never completed.
Since then the site has been transformed into a residential property with no public access.
But the historic Fort is back on the public market with estate agents Savills – and has received offers in excess of £1.5 million.
The fortress itself extends to approximately 8.3 acres, which includes The Guards’ House – a two bedroom property with the potential to be extended.
At the front of the house is a small turfed garden and to the side are four former large water tanks – two of which have been converted to workshop space which could provide additional accommodation.
Within the heart of the fort lies the Officers’ and Sergeants’ Mess which has undergone a recent refurbishment.
Partly built into the defences, the space comprises a wide entrance hall off which there is a kitchen and a drawing room – both with feature arched windows overlooking a courtyard.
The property also has two bedrooms and a bathroom – the latter of which houses a recycled shower which started life on retired British ocean liner, Queen Elizabeth 2 (QE2).
On the first floor lies the main bedroom with steps up to the ramparts, which enjoy views over the Medway Valley.
And at the centre of the base are nine former casemates – fortified gun emplacements – which were once used as a lodge for the soldiers based there and now provide stables and storage space.
There is also a large parking area to the east of the site which has recently been renovated, along with a small secure compound that is currently let.
The current owners, who are looking to downsize after a labour of love spanning two decades, have used the unique layout and size of the subterranean network to create a number of spaces that have been used in various film and music video shoots in recent years.
Baywatch star David Hasselhoff filmed his six-part mockumentary series ‘Hoff the Record’ at the site in 2014.
To add to the intrigue, the tunnels lead down to the old magazine chambers where the owners have created their own private bar and entertainment area.
Chris Spofforth, from Savills, said: ‘Without question, this is one of the most unusual sales I have been instructed on in my career.
‘Not only does it have a wealth of history, Fort Borstal also presents an utterly unique opportunity to acquire a one-of-a-kind site that offers an exciting renovation or redevelopment project that brings with it an array of possible future uses.
‘This spectacular and diverse property, the likes of which may not be seen again, is complemented by the viticulture, equestrian, natural capital and leisure potential of the sale, subject to the necessary consents.
‘Communications across Kent have improved significantly in recent years and the area is particularly popular, not only in terms of the property market, but with both domestic and international tourists with its proximity to European transport links and to the Heritage Coast.
‘There is such outstanding variety and opportunity within Fort Borstal and we are anticipating a very high level of interest from across a wide spectrum of potential buyers