The high-speed crash which nearly killed 'Top Gear' presenter Richard Hammond was probably caused by a nail in the tyre of the vehicle he was driving.
According to an official BBC report, there is a "distinct possibility" that a check of the tyres between earlier practice runs could have identified the danger.
The report concluded an "inability to spot the damage to the tyre" was the underlying cause of the accident, in which Hammond sustained a serious brain injury.
He was on his fourth run and driving at speeds of nearly 300mph when the front offside tyre suffered a "catastrophic disintegration".
A penetrating object such as a nail, probably picked up during the course of the day's events, punctured the side wall of the tyre.
The BBC's 88-page report said Primetime Landspeed Engineering (PLE), the company which supplied the jet-powered Vampire drag racer, had sole responsibility for the car's safety.
But it criticised the 'Top Gear' team for having no "assurance system" to ensure PLE's safety checks had been carried out properly.
The report said of the crash: "The indirect cause was the inability to spot the damage to the tyre, possibly due to either the lack of an adequate checking procedure or inadequate implementation of the procedure by PLE as the 'experts' with sole responsibility for the safety of the car; and to a much lesser extent 'Top Gear' not having an assurance system to ensure that the safety checks were being performed on the day."
There was inconclusive evidence on whether the safety checks were conducted "to an appropriate standard".
The report also said: "It is the provisional opinion of the tyre expert, pending further information from PLE, that a detailed examination of each tyre immediately following each run is likely to have revealed the area of weakness on the front off side tyre."
"It is also a distinct possibility that examination of the tyres between earlier runs should/could have identified the presence of the penetrating object which the tyre expert believes led to the failure of the tyre."
"The Top Gear team... did not have anyone with sufficient knowledge to assess the adequacy of the checks made by PLE on the day of the shoot."
It added: "Where the the BBC relies on 'experts' (people with specific knowledge/skills) with prime responsibility for safety issues for high risk activities there is a need to ensure the BBC has selected competent persons and that it provides an appropriate level of assurance that these responsibilities are being discharged adequately."
The report praised 'Top Gear's production team for areas of good practice, including a decision to drop the original idea of attempting a land speed record because it put Hammond at greater risk.
A report by the Health and Safety Executive in June identified failings in the BBC's safety management systems.
