The car crash involving the vehicle carrying the prime minister and his police escort in Wellington last year was caused by another vehicle coming around a roundabout towards them at speed, resulting in the prime minister's car braking hard and the police vehicle colliding with it.
An investigation was launched after a police vehicle crashed into the rear of the Crown car carrying Christopher Luxon and Finance Minister Nicola Willis as they headed to catch a flight at Wellington Airport in November.
The police report, obtained by RNZ under the Official Information Act, shows police chalked up the incident on Cobham Drive as a "genuine mistake," and that while police were technically at fault, attending staff made good decisions.
The report noted the two vehicles had stopped at the 'give way' sign for the Troy Street roundabout.
The roundabout was initially clear, so they proceeded, but then another vehicle "suddenly appeared at speed" on the roundabout.
The driver of the front vehicle, a BMW 7 Series, suddenly braked hard, and the second vehicle, a Toyota Highlander, collided with it.
"Both vehicles had stopped to check the way was clear on the roundabout. The driver of the rear vehicle... is technically at fault for colliding with the rear of the front vehicle..., as they moved off, but there are mitigating circumstances with the sudden arrival of the unidentified vehicle on the roundabout," the report said.
The police supervisor wrote that consideration was given to a written traffic warning or an infringement offence notice, but they did not believe it was required "given the minor nature of the collision and the reason for it".
Crown vehicles are reserved for the travel of the prime minister and other ministers and officials.
Neither Luxon nor Willis, travelling as passengers, were hurt.
Speaking after the crash had occurred, the prime minister described it as "a minor shock" but that he was "all good."