He slid off the track and collided with a heavy tractor that was in the process of removing another car from the tyre barrier.
That was the verdict of an International Automobile Federation report announced on Wednesday Dec 3 2014). The 396-page report, released on the federation's website, read: "Bianchi did not slow sufficiently to avoid losing control at the same point on the track as (Adrian) Sutil."
'MEDICS' SPEED SAVED HIS LIFE'
Bianchi's is the most serious F1 race injury since the death of Ayrton Senna in 1994. The Marussia driver, whose British-based team is no longer in business, remains unconscious and in a critical condition in hospital in southern France after being flown home from Japan in November 2014.
VIDEO: Watch the Bianchi crash
Back in October the Marussia team expressed "shock and anger" after news media reports suggesting that Bianchi had not slowed sufficiently under the caution flags.
The report added: "If drivers adhere to the requirements of double yellow flags then neither competitors nor officials should be in immediate physical danger. Bianchi over-controlled the oversteering car, such that he left the track earlier than Sutil, and headed towards a point 'up-stream' along the barrier.
"Unfortunately, the mobile crane was in front of this part of the barrier, and he struck and ran under the rear of it at high speed."
Earlier versions of this story used the year 2015 in error. Sorry, guys!