Thursday 26 June at 15:55 : A meticulous joint investigation into the cause of Heikki Kovalainen's Barcelona crash has finally got to the bottom of why the McLaren driver was pitched into the barriers during the Spanish grand prix.

It was originally speculated that the Finn's accident was caused by a sudden, catastrophic, structural failing of the left-front wheel rim.

McLaren chief executive Martin Whitmarsh later added that, based on initial trackside evidence and speculation, stones or debris coming into contact with the wheel could have triggered the structural damage.

At the same time, an exhaustive investigation, in collaboration with wheel supplier Enkei and the FIA technical team, was launched.

"The investigation not only involved thorough scrutiny of the telemetry data and a microscopic analysis of the surviving components, but also a simulated reconstruction of the event back at the McLaren Technology Centre," Whitmarsh said at the Silverstone test this week.

He explained that the investigation showed that a central area of the rim had been left unmasked before being sprayed with lacquer -- a common practice to improve the efficiency and longevity of components.

The resulting lacquered surface significantly reduced lock-hold on the wheel rim.

This meant that the wheel and axle on Kovalainen's MP4-23 began to move apart under high cornering loads, leading to rubbing against the brake drum, fatigue, and a failure of the rim's inner lip.

"We now thoroughly understand how the failure occurred; not, as was originally reported, as a result of a wheel failure but by the incorrect application of a lacquering process which was beyond the control of our wheel supplier, Enkei, with whom we have enjoyed a fantastic relationship for more than 10 years," Whitmarsh added.

He said procedures have been put in place to ensure the incident cannot repeat.