The £4,000 balloon covers an outdoor swimming pool and is included in the sale of Hazel and David’s four-bedroom home in Hillgrove Gardens, Kidderminster.

The couple have decided to sell up and down size after it became too big for them.

The Parkers had a 12-metre long pool built in 1996 complete with a tent cover to keep out the cold and debris.

Within a year it was damaged during a storm so the Parkers replaced it with a plastic bubble dome, made from darkened PVC, which looks like a spaceship when illuminated at night time.

It is kept warm by a heater which runs all year round and keeps the dome at a constant temperature of around 20 degrees celsius. The dome is inflated by an air pump which keeps the structure upright.

Mr Parker, aged 63, a retired carpet salesman, used the pool to aid his rehabilitation from a car crash in 2001.

He said: “It’s lit up like a spaceship at night and looks really sci-fi. People come to have a look at it because they think it’s a flying saucer.