A DEVOTED couple died after their motorbike hit a motorway barrier - but the reason for the collision will remain a mystery, a coroner ruled this week.

Amanda and Nick Hall died at the scene of the crash on the M40 after their motorcycle veered off the carriageway and glanced off the roadside barrier, sending their vehicle spinning more than 150 metres down the road.

But an investigation showed there were no defects with the Marlow couple's vehicle that would have been a contributory cause to the accident.

And coroner Richard Hulett said, despite the fact the Halls were travelling at at least 83 mph at the time of the collision, the motorcycle was not being ridden recklessly.

The accident happened on the southbound carriageway of the M40 between junctions 5, for Stokenchurch, and 4, Handy Cross, shortly after 1.30pm on Thursday, August 1. The couple, who had recently celebrated their 30th wedding anniversary, were pronounced dead at the scene from severe injuries sustained in the collision.

Motorist Sam Warwick told the inquest at Beaconsfield Coroner's Court yesterday 49-year-old Mrs Hall appeared to be looking down at the rear wheel of the bike, as if there was something wrong with it.

He said: "She was holding onto the rider even more tightly. I got the impression the rider wanted to look down as well. He leaned to the left and I wondered if they were communicating.

"The bike wasn't swaying about, it looked fine to me.

"It veered to the left towards the hard shoulder. I thought he would come to an abrupt stop on the hard shoulder. He didn't appear to slow down either, as I wasn't catching it up."

Mr Warwick added: "The bike hit the barrier head on and smashed into lots of pieces that went all over the road in seconds."

Neither Mrs Hall, who was the pillion passenger on the back of the bike, nor her 51-year-old husband were wearing protective bikers' leathers but both were wearing helmets, the inquest heard.

Collision investigator Daniel Henderson said the motorbike's tyre pressures were around 25 per cent lower than the manufacturer's recommended guidelines and the suspension was softer than it should have been, but he said neither of those factors would have contributed directly to the crash.

PC Henderson added there was no evidence Mr Hall had tried to apply the brakes and said tests showed he would have been riding somewhere within the region of 83-92 mph.

Recording a verdict of death by road traffic collision, coroner Richard Hulett said: "I'm afraid we've got a degree of mystery as to why it happens. The core events are quite clear and the reasons are anything but clear.

"It looks to me as if the rider was heading towards the hard shoulder for some concern he had - I don't know what it was because there's no evidence - and in the process it was slightly overdone with the catastrophic result they were both thrown from the bike."