The death of a mum of two in a motorbike crash on the M25 remains a mystery following an inquest today.

Sally Crosby was airlifted to hospital in London after crashing her motorbike on the anti-clockwise carriageway between junction 4 for the A21/A224 and junction 5 for the M26/A21 near Sevenoaks.

She had been riding alongside two other bikers, including husband Colin when the tragedy happened, in April.

An eyewitness described seeing Mrs Crosby moving smoothly from the middle lane of the motorway to the inside lane and then continuing towards the crash barrier as though there was another lane.

The inquest, held at Gravesend Old Town Hall today, heard from Sgt Hannah Brown from Kent Police's Serious Collision Investigation Unit.

She found the bike had a low level of brake fluid and a problem with the front tyre, but said neither had contributed to the accident.

No other vehicles were involved in the crash and there were no road defects or visibility issues.

Mrs Crosby was said an experienced rider, and the possibility of her having fallen asleep was deemed unlikely.

Sgt Brown described the accident as "almost inexplicable".

One side of the motorway was completely closed following the incident, on April 9, to allow an air ambulance to land.

She was initially treated by a passing off duty police officer before being airlifted to St George's Hospital, where the 46-year-old carer from Southampton spent nine days in a coma.

Despite efforts made by staff at the neurological intensive care unit to save her, family members were told nothing more could be done.

The mother-of-two continued to breathe by herself for 26 hours after being removed from life support machines.

Senior coroner Christopher Sutton-Mattocks said: "This is a very sad incident involving the death of a motorcyclist on the M25.

"Mrs Crosby was riding the motorcycle in lane three of the motorway when for a reason which has never been clear crossed the line into the area between the third lane and the crash barrier."

He concluded Mrs Crosby had died as the result of severe head injuries caused by a road traffic collision.

Motorists were criticised at the time of the crash after a number were pictured playing football on the clockwise-carriageway, which was closed to allow an air ambulance to land.

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