A comprehensive internal report has revealed more details on how Jari-Matti Latvala and Miikka Anttila were able to escape injury in their dramatic accident during the Rally of Portugal.

The pair were leading the event at the wheel of their BP Ford Abu Dhabi Ford Focus WRC when they went off the road and rolled 200 metres down a hillside – although both driver and co-driver were able to escape unscathed.

The report, prepared by Latvala's engineer Tim Jackson, goes into detail about how the strength of the car had prevented any series injuries in one of the most dramatic WRC events in recent years – with some parts of the bodyshell even in a position where they can be rebuilt and used again later in the year.

"As horrific as this incident appears from the video recordings, the safety structure of the car performed excellently and precisely as designed in protecting the driver and co-driver,” he said. “The use of relatively ductile materials such as T45 Steel for the roll-cage meant that the steady – but limited – deformation of the roll cage structure not only absorbed sufficient energy to protect the occupants, but also that the many undamaged areas of the body shell can be rebuilt and used again.

"The introduction of increased safety measures – both by regulation and design choice – have proved to be beneficial in the incident, meaning that the driver and co-driver were both able to walk away uninjured.”

Data showed that the accident, 9.1km after the start of the fourth stage, began when 24-year-old Latvala began to brake on a crest which hid a left-hand corner.

First the rear and then the front of the Focus RS WRC hit the bank on the inside of the corner, flinging the car over a roadside barrier and down the hillside, gathering momentum as it barrel-rolled. The bonnet and tailgate became detached while Latvala's door opened and was crushed during the rolls.

The car stopped rolling when it hit a tree, without which it is expected the accident would have continued for a further 50 metres. The incident lasted 19.8 seconds with the car completing twelve full rolls. Despite the violence of the crash, the report reveals that the shape of the cockpit area was 'maintained excellently'.

"Basic measurements show that there was no deformation into the cockpit of the main roll hoop joint,” Jackson continued. “The A-pillar and door bar roll cage structures remained virtually undamaged on both sides of the car with only very small deformations evident. The main hoop tube, located close to the B-pillar buckled slightly on the driver' side whilst the C-pillar body panel structure, unsupported by roll cage tubes, flattened to a shallower angle. However, none of these was sufficient to pose a danger to the crew."