Anaesthesia experts have debunked claims that French robbers used sleeping gas on Formula One star Jenson Button and his wife during a burglary.
The 35-year-old racing star and his wife Jessica were feared to have been knocked out by gas pumped into their luxury villa on the French Riviera, leaving them helpless as thieves seized her £250,000 engagement ring on Monday night.
A source told 'The Sun' newspaper: "Police have told Jenson they're convinced the burglars gassed the house using the air-conditioning units.
"Jenson is convinced that's what happened too. The burglars were in the same room as him and Jessica, rifling through all their drawers.
"But they weren't disturbed at all because the effects of the gas gives the burglars free rein."
There were reportedly three other people in the property at the time who were also affected by the gas.
But a spokeswoman for the Royal College of Anaesthetists has poured cold water on the claims, saying such a scheme would be nearly impossible.
"Our view is that it is very unlikely because it would be so impractical," she said. "You would need to use a truckload of gas, and that amount would be phenomenally expensive to obtain.
"One has to ask why anyone would spend so much money on what is such an impractical method".
The gases are so pungent that the victim would be able to smell it even if they were asleep, she added.
The robbery is the latest in what seems to be a spate of gas attacks on wealthy celebrities on the French Riviera.
In 2006 the French footballer Patrick Vieira fell victim to a similar robbery, where thieves reportedly pumped gas into his property's air vents before fleeing with jewellery and his Mercedes.
The former Arsenal captain and his wife Cheryl, as well as their daughter, all awoke with splitting headaches and immediately knew something was wrong, according to reports.
Five people were arrested in connection to the theft in Nice and investigators later tracked down the missing 4x4 vehicle.
The fashion gurus Trinny Woodhall and Susannah Constantine were prey to a similar attack four years later in Cannes, where they were allegedly smothered with chloroform.
Thieves crept into the 'What Not To Wear' presenters' villa and clamped chloroform-soaked pads onto their mouths, robbing them of jewellery and cash as they slept, it was claimed.
Experts say it is unclear whether the robberies were all committed by the same gang, pointing out the incidents took place over a number of years.
It was also speculated that the robbers behind the 2006 and 2010 robberies passed on their skills to a younger gang who carried out the attack on Mr Button.
Professor Michael Levi, an expert in security and organised crime at the University of Cardiff, said he suspected the gang bought the drugs on the black market from a corrupt medic or chemist.
Speaking to the 'Telegraph', he said: "In this case it may be that you have a gang of relatively low-level criminals working with or being supplied by a chemist who has expertise on how to administer the gas without harming anyone.
"There is obviously a risk in that if you don't administer the dosage correctly you could kill someone, or they could wake up in the middle of what you are doing," he said.
"The key question is where this gas is coming from, and I expect they will have been looking for it in hospitals, or at large suppliers, and will have approached someone like a medic, or perhaps a former medic, who is willing to sell it to them."
The Royal College of Anesthetists issued a similar statement last year amid claims that Britons were being gassed and burgled in motor homes.
It read: "Despite the increasing numbers of reports of people being gassed in motor-homes or commercial trucks in France, and the warning put out by the Foreign Office for travellers to be aware of this danger, this College remains of the view that this is a myth.
"It is the view of the College that it would not be possible to render someone unconscious by blowing ether, chloroform or any of the currently used volatile anaesthetic agents, through the window of a motor-home without their knowledge, even if they were sleeping at the time.