Joanna Ledwidge, 40, was yesterday undergoing blood tests, including one for HIV, following the assault. It was the most vicious in a recent spate of thefts from vehicles in rush-hour tailbacks on and around the A40 in west London. At least 12 similar incidents have occurred along a two-mile stretch of the busy dual carriageway during the last two weeks.
Mrs Ledwidge was preparing to join the A40 from Bloemfontein Road in Hammersmith, at about 7.30pm on Tuesday.
As she queued in slow-moving traffic two teenage boys approached her red Alfa Romeo car, one on each side.
The first teenager opened the unlocked passenger door and grabbed her handbag and mobile phone. Mrs Ledwidge took hold of the bag but as she struggled the second teenager entered through the driver's door and bit her on the face and ear. She was also punched several times before she released her bag.
Mrs Ledwidge was said to be greatly distressed by her ordeal.
Her attackers are described as both black, aged about 16, slim and about 5ft 8in tall. One had dreadlocks and was wearing grey tracksuit bottoms and a bomber jacket, while the other wore a baseball jacket and dark tracksuit bottoms.
The A40 first became notorious last year as an area favoured by 'carjackers' who have imported the crime from America. Last September, BBC managers warned staff working at television headquarters in White City - alongside the trunk road - to avoid the inside lane after a spate of thefts.
One attack involved Sir Colin Marshall, chairman of British Airways. A window was smashed in his Daimler, but the attempt to steal his mobile phone was unsuccessful.
Similar thefts from stationary vehicles have also been reported in the Old Kent Road in south-east London. However, the assault on Mrs Ledwidge - one of three in the area within hours - has caused detectives particular concern as it is the most violent such theft to date.
A senior police officer involved in the case said: 'In most cases someone has just leant in and taken something, either a handbag or a mobile phone. Only on a couple of occasions was any violence offered.'
Detectives believe several groups are preying on drivers using the A40. They work mainly during the evening rush-hour and often target high-performance vehicles with a lone occupant.