The son of BBC Antiques Roadshow expert Eric Knowles was killed instantly when he drove his car into the back of a lorry at nearly 100mph, a coroner heard today.

Sebastian Knowles died in the accident in the early hours of the morning when his car was dragged under the wheels of a foreign-registered lorry while driving along a motorway.

At the inquest in Beaconsfield, Coroner Richard Hulett heard that the 26-year-old had been driving north in the motorway's middle lane before inexplicably crossing into the inside lane hitting the lorry.

There was "no obvious reason" why the bank manager would have driven his white Mercedes C220 into the lorry, but could have momentarily fallen asleep at the wheel or been temporarily distracted, Mr Hulett said.

Mr Knowles, who also worked as a DJ under the guise DJ Seb.K, was killed instantly hitting the Austrian-registered lorry laden with apples on the M40 motorway near Beaconsfield, Buckinghamshire. He also played gigs under the moniker DJ Sparky B and had worked with big names including The Artful Dodger and Ultrabeat.

A police investigation showed the lorry was driving at around 40mph in the inside lane just before 3.30am on May 1 this year.

Accident investigators concluded Mr Knowles would have been driving at 96mph just before he ran into the lorry and was pronounced dead at the scene. A post mortem examination showed his skull had been fractured. No traces of alcohol or drugs were found in his system.

Collision investigator Andy Evans of Thames Valley Police said although Mr Knowles was driving at speed, it was not the major cause of the collision.

"It's by a momentary loss of concentration or a distraction," he told the hearing at Beaconsfield Coroner's Court, Bucks.

"I can't rule out fatigue as playing a part in this collision. The speed aspect played no part in the collision."

Recording a verdict of death by road traffic collision Mr Hulett said: "It's inevitable we will speculate, all of us, as to why on Earth this has happened.

"This is probably down to fatigue, or some momentary loss of concentration.

"There is no explanation why he wouldn't have just driven past this lorry. He's veered to the left for no obvious reason - that has to be something to do with the driver. He could possibly have fallen asleep at the wheel - it could have happened.

"The consequence, of course, was one of immediate death. It's a massive collision."

Mr Hulett concluded that Mr Knowles, of Lysander Close in Woodley, Berks., died as a result of a road traffic collision.

His father, the TV expert, was not present at the inquest, but his fiancee, Nina Porter, attended.