ROCK stars heading for that last Great Gig in the Sky often go out with a bang. But when the so-called Wild Man of British Pop, Keith Moon, overdosed on pills in the 1970s, he made his exit from a discreet, almost nondescript pied-a-terre in the heart of London's Mayfair.

The two-bedroom flat, perched on the top floor of 9 Curzon Place, belonged to the American singer-songwriter Harry Nilsson, whose 1971 hit Without You became a 20th-century standard.

It is perhaps surprising that the place has not become some sort of rock shrine. Four years before Moon the Loon was stretchered away, another pop music titan, Mama Cass Elliot, died in the same flat while staying in London. Jinx? Or just coincidence?

Property manager Richard Henderson summons all his reserves of diplomatic sangfroid: "It's not really a problem," he explains. "To the average Englishman, death is simply something that happens.

"Some overseas buyers tend to be rather more nervous about it, particularly the notoriously superstitious Chinese. But it's more of a problem with places associated with death, such as converted hospitals."

It was a handy address for the high life - the Playboy Club and assorted casinos are just a three-minute stagger away - but the Grade II listed, 18th-century house at 9 Curzon Place is no Georgian gem. The front of the property, of blackened London brick, is clumsily relieved by an awkward-looking two-storey oriel, picked out in cream stucco.

The house was gutted just after the Second World War, a lift shaft brutally thrust up the central stairwell and a dozen apartments created. Nilsson would have enjoyed total privacy, and his guests would have flitted in and out through a discreet front door, beneath a handsome fanlight.

Mama Cass Elliot was not a natural flitter; although only 5ft 5in tall, she weighed about 15 stone. A former member of the Mamas and Papas, she was in Britain in the summer of 1974 to star at the London Palladium.

One day in late July, the lift at 9 Curzon Place carried Cass up the four floors to Flat 12. It was to be her final ascent. She was found dead in the bedroom, the victim of a heart attack and the prolonged effect of obesity.

Rumours flew that she had choked to death on a ham sandwich, but pathologist Professor Keith Simpson found no traces of food blocking her trachea. Mama Cass, whose real name was Ellen Naomi Cohen, had died of natural causes at the age of 32.

Victim: Keith Moon died at 9 Curzon Place

It is nearly 10 years since the flat was last occupied, and the place is a wreck. In the main bedroom, a pair of grubby green curtains hang limply at the window overlooking (or rather overlooked by) the neighbouring London Hilton. Debris spills out of the built-in wardrobes. Paper and telephone directories lie strewn on the floor. Wall lights hang crazily askew.

"It's certainly a mess," says Mr Henderson, leading the way through the living-room to the tiny balcony, from where you can catch a glimpse of the London skyline. "But in a couple of years, this will be one of the smartest apartments in Mayfair."

The Greek billionaire John Latsis has bought this and neighbouring properties to turn them into a £120 million development of houses, flats and offices. Demolition is well under way, and while listed property in Curzon Place - including this one - stays put, it won't be long before its innards are torn out and the house is remodelled.

Flat 12 is in its death throes. Mama Cass may have been one of its weightiest occupants, but four years later came the craziest. Keith Moon, legendary drummer with The Who, was one of the most flamboyant characters in rock. Bingeing on drink and drugs, famously driving his lilac Rolls-Royce into a swimming pool (in fact, his own garden pond), Moon the Loon was an exploding time-bomb.

As his biographer, Tony Fletcher, observed, Moon "threw his head into the cavernous jaws of certain disaster time and again, tempting fate with an almost unparalleled intake of alcohol and drugs, and emerged on every occasion (but the last) just about whole."

That last brush with fate happened at 9 Curzon Place, once again in the bedroom at Flat 12. In the late summer of 1978, Moon was living there - courtesy of Harry Nilsson - with the model Annette Walter-Lax. On the evening of September 6, the couple attended a film-launch party, returning to Curzon Place for a late supper. Moon took some Heminevrin, medication for countering the symptoms of alcohol withdrawal. He began to watch a video, but fell asleep, zonked by a combination of pills, wine and the late hour.

He woke next morning and asked Annette to make him breakfast. When she complained at being asked to get up in order to cook another meal, Moon snapped: "If you don't like it, you can f*** off!" - his last reported words.

After eating a steak, washed down with more Heminevrin tablets, Moon and his girlfriend went back to sleep. Later that afternoon, when Annette tried to wake him, her lover lay lifeless in the bed. She tried to revive him and called a doctor, but Moon was dead on arrival at hospital. A fortnight before, he, too, had turned 32.

Once again, it was Prof Simpson who performed the post mortem. Of the 32 Heminevrin tablets he found in Moon's stomach, 26 were undissolved. "The quantity was enormous," Prof Simpson reported, "and constituted a vast overdose." A half-empty bottle of 100 Heminevrin tablets was found at Moon's bedside at Curzon Place. The coroner recorded an open verdict.

Other Who members were incredulous. Pete Townshend said Moon had "always appeared so close to blowing himself up in the past that we've become used to living with the feeling". John Entwistle believed Moon tempted fate once too often. "I think someone looked down and said : 'Okay, that's your ninth life'."

Flat 12 faded back into anonymity when Nilsson sold it. Its subsequent inhabitants gave it a 1980s makeover of gold flock wallpaper and silk curtains in the drawing-room, but the foil-effect walls in the kitchen and the peach-coloured bathroom suite are still pure 1970s kitsch.

"This was not a high-quality conversion," says Mr Henderson, pointing out the gimcrack finish, "but it was typical of what the undemanding English used to settle for. In the 1990s, the huge increase in foreigners buying Mayfair flats had a big effect on improving standards."

The configuration inside 9 Curzon Place will completely alter during the new development, and what are now three flats on the fourth floor will become two luxury apartments. These will be offered on 125-year leases, and the whole scheme, complete with pedestrianised square and underground car park, is due for completion in July, 2002. At £1million plus, prices of individual flats will remain firmly in the rock-star range.

There was an odd echo to Moon's death. As with Mama Cass, there were wild stories about choking, a theory concocted, in Mr Fletcher's view, by osmosis. But Mr Fletcher also quotes "certain insiders" as saying that on that night, Moon had a famous visitor at Curzon Place. Did the mystery celebrity bring drink or drugs that finally sent Moon over the edge?

"That famous person is now also dead," writes Mr Fletcher, "which of course means they can't verify or deny. And Annette is absolutely adamant that no such visit took place." Perhaps, as the late Nilsson once famously sang, that's just the way the story goes.