Bruce McLaren and Wally Willmott during the New Zealand Grand Prix in 1964.

At 21 years of age, Wally Willmott was living the petrolhead's dream.

In 1961, Willmott finished his five-year apprenticeship with Young Brothers in Timaru when he walked out the door to follow the motor racing circuit for a few months while he figured things out.

Little did he know, a few months of motor racing would turn into a lifetime obsession after a chance meeting with a young driver named Bruce McLaren for whom he would later work.

CHRIS MCKEEN/FAIRFAX NZ Wally Wilmott, of Southland, one of Bruce McLaren's earliest mechanics, was at the NZ premiere of Unfiltered, Roger Donaldson's movie about the NZ car maker.

Speaking before the national premiere of the Roger Donaldson-directed documentary McLaren in Auckland on Tuesday, Willmott said he had not seen the film yet and was "s...ting himself quietly".

"I was a petrolhead; I had a strong interest in motor racing."

When asked what McLaren would make of the movie he said he thought he would be as amused as he was at the idea they would feature on the big screen.

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Willmott was the first mechanic McLaren chose when he established the McLaren Racing Team in the United Kingdom, one of the most successful in Formula One championship history.

He worked closely with McLaren from 1961 to 1968 and helped McLaren design and build the first McLaren race car in 1963, Willmott said.

His first experience in the pits at F1 level coincided with McLaren's victory in the 1962 Monaco Grand Prix.

Willmott had worked with Donaldson on the documentary and said he expected to appear quite often in it.

The world of F1 racing had come along way since the days when he and McLaren would build the race cars from a pile of metal.

For the past 10 years, Willmott has been living in Otatara, just outside of Invercargill, where he happily works away on his historic racing cars.

In 2006, he travelled back to Invercargill to to be part of a tribute to motorsport legend George Begg that was put on by the Southland Sports Car Club.

Begg constructed world-class racing cars in rural Southland in the 1960s and 1970s.

"I came down to lend a hand to help with the tribute and never left."

An Invercargill showing of the documentary will be held on Thursday.