The site of an abandoned former prison looming over Dover could be transformed into a hotel and leisure centre.

KentOnline reporter Sam Lennon had an exclusive tour around the Citadel at the Western Heights, and spoke to bosses about their ambitious plans...

You could almost hear the cell doors slamming.

This was the grim impression inside Rye House, the main custody building at the Citadel in Dover, once used by the prison service but now long-empty.

The main hall, with a mesh ceiling to catch someone falling or being pushed, remains as it was left. It's the same with the poky cells, stripped of furniture but with their toilets and wash basins intact.

The hall and building were empty but still there were moments when I could sense the menacing, pressure cooker atmosphere of a prison.

KentOnline was granted an exclusive view inside the Citadel, which is otherwise shut off to the public.

The complex developed from the late 18th century as a fortress, particularly to resist invasion from Napoleon's forces.

From the 1950s to the 2010s it was a prison, borstal and then an immigration detention centre.

David de Min, whose company Dover Citadel Ltd now owns the site, says: "It was used to keep people out and then used to keep people in."

The Citadel sits on top of the Western Heights and is out of sight, out of mind to many locals. It lies flat on one of the highest points of Dover so cannot fully be viewed from the tops of neighbouring steep hills.

Yet the brownfield site, in 33 acres with 54 buildings, is expected to be transformed over the next decade with small business units, a hotel and possibly a leisure centre too.

Mr de Min, the company's chief executive, said: "We are looking to create something that has not been done before.

"We've got this incredible asset here and we are looking to try to repurpose it to create something that's not only for the local benefit but also for bringing people down to Dover.

"I've always seen Dover as a sleeping giant. It's got so much potential.

"But being the busiest passenger port in the world, a lot of people unfortunately just pass through.

"But if we can capture even just a small part of that, that would be amazing."

The complex is still used for filming and the Rye House hall was a location for Danny Boyle's TV drama Pistol, based on the life of Sex Pistols guitarist Steve Jones.

The scene at Rye House shows the band arriving to play to convicts, who first hurl insults at them.

A taunting Johnny Rotten tells them: "Who's coming to the pub after this?"

The replies included: "You'll get your head kicked in."

Then the band splutter into Anarchy in the UK and the lags are eventually won over, nodding their heads to the fiery music.

Rye House ended up as the main custody building, and there also remain three identical accommodation blocks, which are believed to have been built around the 1970s.

They were called Sandwich House, Romney House and Hastings House.

Overall the maximum capacity for inmates at the Citadel was 850.

The Citadel had been in military use since its development, also used as barracks during both world wars, but the prison service took it over in 1952.

It was first an adult jail and from 1957 a borstal, in later years remodelled as a Young Offenders’ Institution.

From April 2002 to November 2015 it was Dover Immigration Removal Centre, still run by HM Prison Service.

It housed about 600 adults appealing for official asylum seeker status - or awaiting to be deported.

The centre then offered televisions and telephones, a gym, a library, a church, mosques and multi-faith rooms.

The theme of law and order at the Citadel continues with a heavy police presence to this day.

Close to the prison blocks is a current training site for both the Metropolitan Police and City of London Police.

The most impressive building in the complex is the two-storey Officers' Quarters, built in 1861.

It is planned to be be part of a 200- to 250-room hotel complex, providing 60 to 80 of the rooms.

Mr de Min said: "It was built to be one of the last points of defence. The walls are a metre-and-a-half thick and it was built to be bomb proof.

"It's a very impressive building and one of a kind and we want to use it as a hotel to allow other people to enjoy it.

"One of the things that is key for us is that this is a very much heritage-led design.

"We are trying to design something that is in keeping with the heritage to maintain the upkeep of this place but also something that is going to add to the whole site.

"This is an ancient monument and we are not plonking a big shiny development.

"We have taken a lot of time to understand the site and work with the forms of the design and use that as our interpretation."

The rear of this distinctive Tudor Gothic style building can been seen from outside the Citadel boundaries from a public footpath going toward Aycliffe.

I was taken on a guided tour of this building too and from the inside it was also grand with its long hallways, huge conference rooms and spacious accommodation.

The top floor of the building had rooms for officers, while their servants lived on the bottom floor.

Research from English Heritage has found that there were originally 18 rooms for officers and nine for servants, suggesting that the latter lived two to a room.

The Officers' Quarters was used as an administration block when it was a Young Offenders’ Institution.

I was also able to view one of the Napolenic water towers, with wells about 450ft (137m) deep and with capacity for 8,800 gallons (40,000 litres) a day and giant tanks at the top.

Mr de Min said: "Because this was a Napoleonic fortress they needed their own water supply. At the time these were among the deepest wells in the UK.

"We'd love to try to utilise that water to have our own supply for the development as part of our own sustainable eco-system."

As for the future of the Citadel, it is expected to have a full rebirth over the next decade.

This spring planning permission was given to open six small business units, which is the first step in a wider development by the present landowners Dover Citadel Ltd.

This scheme, estimated at £80 million to £100 million, is expected to progress over the next eight years.

Planning applications are now due to be submitted for the hotel, a cycle track and leisure centre.

Few details are available at present and it is not yet clear what form the leisure centre will take.

The detailed plans also involve also getting permission such as scheduled monument consent.

Dover Citadel Ltd is working on the scheme with groups such as Historic England and Dover District Council.