The night before he died Heath Ledger was spotted at one of his most regular haunts, the fashionable Beat-rice nightclub, a low warren of dark corners and mirrored walls in New York’s West Village. It is owned by the actress Chloë Sevigny’s family and is a haunt for rockers such as Courtney Love and REM’s Michael Stipe.

The 28-year-old Australian expressed his usual public shyness in style: he wore a ski mask – with holes cut out for eyes and mouth – and a hood over his head, according to a waiter.

“People thought he was just playing around, but it was a bit intense.” Ledger had frequently been spotted in other louche Manhattan nightspots such as Bungalow 8 and Marquee – in the colourful company of gossip-column regulars such as the designer Marc Jacobs, who came out of rehab last year.

People magazine, the supermarket tabloid, claims that since last September, when Ledger moved out of the family home in Brooklyn he had shared with his Brokeback Mountain co-star Michelle Williams and their baby daughter, he had become a fixture on the New York party circuit, “drinking and taking drugs to excess”.

In modern Manhattan “hard partying” is code for late nights, drug use and semi-public sex, a throwback to the preAids, Studio 54 disco days of the 1970s. Only the choice of drugs has shifted. In those days it was cocaine.

These days, drugs sold in urban clubs are often mixtures of legally prescribed antidepressants, which can act as serotonin-boosting “uppers” on a nondepressed brain. Such mishandled drugs kill 20,000 Americans a year, nearly twice as many as 10 years ago, a rise driven by youthful recreational misuse.

By comparison, 17,000 Americans die from overdoses of illegal drugs. The day after Ledger died the White House cancelled the launch of a publicity campaign designed to warn parents about prescription-drug abuse, out of “sensitivity” towards the actor’s death. Critics said that if the New York coroner were to reveal that prescription drugs were involved in Ledger’s death then the White House might not have helped its own cause.

The New York medical examiner’s office said last week that the initial postmortem examination of Ledger was inconclusive and that it would take about 10 days to determine the cause of his death. It said the standard procedure was to test for a “spectrum” of legal and illegal drugs.

The prescription drugs reportedly found in Ledger’s apartment included diazepam and alprazolam, which are prescribed for anxiety, as well as Ambien sleeping tablets, a bottle of Donormyl, an antihistamine used as a sleeping aid, and a packet of the insomnia drug Zopi- clone.

All can be taken as part of a recreational drug cocktail selling at many clubs in New York, Miami and Los Angeles as a £25 “pick-me-up”. They are popular among office workers facing increasingly common random workplace drug tests.

Dr Michael Baden, a former chief forensic pathologist for the New York state police who is not involved in the postmortem at the Bel- levue hospital, said that if someone was prescribed pills under a wide variety of brand names for a single purpose, as Ledger was, that counted as drug abuse “and prescription [drugs] are probably more abused than illegal drugs”.

Baden has upset Ledger’s family, friends and fans in Australia – where the actor was idolised – by forcefully stating his belief that the death was not an accident.

“We don’t see many accidental deaths from common sleeping pills,” he said. “You just don’t take one extra pill by accident and die – it has to be 10, 20 or more at a time. That is more than a person might take accidentally, even if they are groggy or forgetful.”

Graeme Plummer, a spokesman for the grammar school Ledger attended in Perth, Western Australia, retorted: “We find it disturbing the way his death has been portrayed by the press. Look, he managed to swallow some sleeping pills and mixed them up a bit. It was an accident. No one here thinks he committed suicide.”

Friends said Ledger drank only water when he returned home to Perth for Christmas.

The Australian artist Vincent Fantauzzo, who persuaded Ledger to pose for a three-faced portrait last month

for the country’s prestigious Archibald art prize, said: “He was very easy and professional to work with. He was not drinking, nor was he interested in drugs. He spoke very positively about his future and future plans. I believe his passing was an accident.”

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