ONCE upon a time living in an oast house was considered quite off the wall ... but that has been well and truly trumped by Paul and Natalie Kidd. visited them in their unique apartment.

When Paul and Natalie Kidd give their address it’s hard not to do a double take. They live in one of the most extraordinary homes in the world - Fort Clarence in Rochester.

This formidable lump of a building was one of the defences constructed along the River Medway to repel a feared invasion by Napoleon. But like the new Wembley Stadium it took a long time to build and by the time it was finished the war was over.

It was used as a military prison and then a lunatic asylum before being taken over by the old GPO and was then converted into four apartments, one of which is home to Paul and Natalie.

With walls a hefty 13ft thick, meandering tunnels and soaring arched ceilings this is definitely a home with a difference. Now it’s up for sale thanks to the latest addition to the family, baby Charlie, a sister for seven-year-old Molly.

The quirky conversion, with its spiral stone staircase, is not ideally suited to a toddler so the family has reluctantly decided to leave.

Paul said: "We wouldn’t move if wasn’t for the littl’uns."

Natalie added: "We will struggle to find something else with so many original features - and such great neighbours. It’s got so much character, it’s not your usual house."

You can say that again. Take the loo off the master bedroom, for example, which provides plenty of scope for dubious jokes. The smallest room was once the shaft used to drop ammunition.

The fortress, listed as a Scheduled Monument, was built between 1808 and 1815 and is rare for having been given permission by English Heritage to convert to living accommodation.

The rooms, converted in the basement, are vast and echoing with a mixture of slate and oak flooring and soaring white painted brick walls and ceilings.

The family’s favourite room is the open plan kitchen cum living cum dining room which features a working fire and a suit of armour, a birthday present for Paul.

Down the somewhat perilous spiral staircase lie the two bedrooms and family bathroom. But that’s not all.

Wend your way through another tunnel and, lo and behold, the arched corridor opens into a games room, formerly the gunpowder room, massive enough to swallow up a full-size snooker table and his and hers exercise bikes with oceans of room to spare.

"This is my play room," joked Paul.

"We’re actually underneath the garden here. I call it the dungeon. The tunnels from here are blocked off but they go for miles to the Dockyard and Fort Luton."

So what are the advantages of living in a fort? "It’s not difficult to heat because of the thick walls," replied Paul. "And it’s nice to show off when visitors come.

"We used to live in suburbia in Walderslade but here we can just wander down to the shops in Rochester."

The massive walls have seen a positive pageant of history.

When used as a military prison, for example, the soldiers were marched along the road to be flogged and allowed to stagger back carrying their coats to ease the chafing of their wounds.

It would not be surprising if a few ghosts are still flitting about the spooky tunnels.

Paul and Natalie say they have both seen the spectral figure of a woman at the top of the spiral staircase.

Paul added: "It’s not difficult to imagine a few unearthly noises when you’ve had a drink!"