Police believe gang had been watching the mansion for days before raid

Jenson Button and his wife Jessica Michibata were gassed at French villa

Jenson Button and his wife Jessica Michibata were gassed at their luxury French villa as robbers looted the house and stole belongings worth £300,000.

The couple - who had been asleep - lay unconscious in bed as the burglars rifled through the rented St Tropez home, taking items including 30-year-old Jessica’s £250,000 engagement ring.

French police believe the gang had been watching the villa for days before letting off a cannister of anaesthetic gas into an air-conditioning vent.

The raiders then broke into the luxury mansion and even walked around the couple’s bed. Three friends who were staying in the rented retreat are also believed to have been rendered unconscious.

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Victims: Jenson Button and his wife Jessica Michibata, pictured, were gassed at their luxury French villa

Precious: Jessica's £250,000 engagement ring, pictured, was among the belongings stolen in the raid

Five days ago Jessica posted a picture of herself lying on the beach while on holiday in St Tropez on Instagram

She also posted a picture of what is believed to be the garden at the villa where her and Jenson were staying

Loved-up: Jenson and Japanese-born Jessica married in Hawaii in December last year after meeting in 2008

The group only discovered they had been targeted when they woke up the next morning and found the mansion ransacked and the engagement ring missing.

Button, 35, who won the Formula 1 drivers’ championship in 2009, has a £71million fortune and was ranked as the third richest British sports star in this year’s Sunday Times Sport Rich List.

A source close to the McLaren driver told The Sun: ‘Police have told Jenson they’re convinced the burglars gassed the house using the air conditioning units.

‘Over the past five years, it’s becoming an increasingly common way for top criminals to launch raids on expensive properties in the area without being disturbed.

‘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 reign.

‘It was the same for their three other friends — they were all completely out of it.’

On holiday: The couple were staying at the property in St Tropez (pictured in file image) with three friends

Terrifying: It is believed that the burglars were in the same room as the Buttons (pictured together in May left). Jessica is pictured right sporting her engagement ring while arriving at the British Grand Prix last month

VICTIMS: WEALTHY BRITONS GASSED AND ROBBED ON THE FRENCH RIVIERA Trinny Woodall (left) and Susannah Constantine (right) were victims of a gas attack in Cannes in 2002 A spate of gas attacks on wealthy visitors to the French Riviera has been noted for at least 15 years, including a 2002 attack in Cannes on Trinny Woodall and Susannah Constantine. The thieves are said to slip through balconies or open windows and direct the sedative into bedroom air-conditioning units. The gangs wear masks to avoid succumbing to the gas before ransacking their victim’s home and stealing any valuable property. Television presenters Trinny and Susannah were burgled after being drugged while they slept during a stay for the Cannes Film Festival. In 2010, British woman Lisa Smyth reported that she and her son were drugged and robbed at the family home in Valbonne, southern France. And in the same year Lucy Mclean and her husband Michael woke in their villa on the Cap D'Antibes to find £30,000 of their belongings had gone, including her engagement ring. Targeted: Patrick Vieira, the former captain of Arsenal Football Club, was also the victim of a gassing burglary at his home near Cannes in 2006 Mrs Mclean, who was 35 at the time, believed the gangs had used nitrous oxide stolen from dentists. French police have previously blamed the activity on Russian or Romanian gangs, who target the conspicuously wealthy. Former Arsenal and Manchester City footballer Patrick Vieira was also the victim of a gassing burglary in 2006, shortly before the World Cup. The ex-France international and his family were knocked unconscious when a gang pumped gas through the air conditioning system of their home near Cannes. When Vieira, now 39, finally awoke he, his wife Cheryl and her daughter had splitting headaches. The family then discovered jewellery and other valuables worth thousands of pounds were missing - along with Vieira's £40,000 Mercedes, which the gang used as a getaway car. Advertisement

Local police interviewed Button, his friends and his wife and are believed to be continuing their investigation by trying to identify the burglars using CCTV.

The group are understood to have been so shaken by the raid that they left St Tropez hours later.

It is understood French police believe two criminals were working together on the robbery and had been staking out the luxury villa for the couple’s entire holiday.

Last night a spokesman for Jenson, who is reportedly in talks about co-presenting Top Gear with Chris Evans, said: ‘Jenson, Jessica and friends were on holiday in a rented villa.

‘Two men broke into the property whilst they all slept and stole a number of items of jewellery including, most upsettingly, Jessica’s engagement ring.

‘The police have indicated that this has become a growing problem in the region with perpetrators going so far as to gas their proposed victims through the air conditioning units before breaking in.

Disappointing: Last month, Button (above on the track) revealed that his future at McLaren remains uncertain

‘Whilst unharmed, everyone involved is unsurprisingly shaken by the events.’

The loved-up couple married in December last year after meeting in 2008.

A spate of gas attacks on wealthy visitors to the French Riviera has been noted for at least 15 years, including a 2002 attack in Cannes on Trinny Woodall and Susannah Constantine.

The thieves are said to slip through balconies or open windows and direct the sedative into bedroom air-conditioning units.

The gangs wear masks to avoid succumbing to the gas before ransacking their victim’s home and stealing any valuable property.

In 2010, British women Lisa Smyth reported that she and her son were drugged and robbed at the family home in Valbonne, southern France.

French police have previously blamed the activity on Russian or Romanian gangs, who target the conspicuously wealthy.