But the mysterious discovery of an alien in his attic has spooked the 54-year-old screenwriter and bewildered extraterrestrial experts, who yesterday suggested the US military could be involved.

The delicate 30cm (12 inch) figure of a baby alien is stored in a pungent liquid and has a US serial number painted on its four-toed foot. Possibly sculpted from a clay-like substance and painted grey, the model closely resembles the aliens depicted in a hoax film of an autopsy of the infamous "Roswell incident".

Curiously, the alien was discovered stored in an old toffee jar wrapped in a copy of the Daily Mirror dating from October 1947. In July of that year, officials at the American air base of Roswell reported and then denied finding the remains of a flying saucer. The Roswell incident sparked a popular fascination with UFOs and led the US air force to collect data on sightings.

One theory is that the alien was left in the loft by a US serviceman working at a nearby US air base. Mr Broom's two-bedroom cottage at Gunthorpe, north Norfolk, which he bought eight months ago, is 45 miles from two large US air bases at RAF Lakenheath and RAF Mildenhall. Many US servicemen and women live and work in the region.

Mr Broom told the Guardian he was "a bit spooked" by the discovery but said he was not yet living in fear of being beamed up by aliens.

"It was stuffed in the corner of the loft with other old newspapers. Before me, an old spinster lived in the house. I don't think anybody had been up there for years. I haven't got three heads and I'm not the sort of eccentric lunatic to think it's an alien but it's a funny thing to find in your loft."

Mr Broom reported his finding to the Sci Fi Channel, who called in Professor Adam Roberts, an expert in science fiction literature, to examine the creature.

"The easy thing to do is dismiss it all and say it's a hoax. It may be or may not be," said Prof Roberts. "The fact that it was found near a US air base suggests there may be a military component to it."

A spokeswoman for the US air force said it had never made such models of an alien, the figure was not government property and the serial number could mean it had been catalogued by a museum. "It's a hoax," the spokeswoman said.

Prof Roberts admitted it could be a film prop dating from the 1960s, but said he was not surprised at US denials: "That is the US air force line. They deny these alien encounters. It is quite possible they concoct stories to cover up for more nefarious activities."

The Sci Fi Channel will this week broadcast live footage of the alien on its website. After further tests, Mr Broom will put it on his mantelpiece.