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There's a film on youtube about Warby I think. As for Britten I know the story fairly well, whilst I don't have anything to do with it anymore my background is in engineering/motorbikes.
For more motorbike stuff there's Peter Williams who was an engineer/rider for Norton back in the day and pioneered the idea of a monocoque chassis and disk brakes. Also a Kiwi guy (seems to be an antipodean theme here...) called Kim Newcombe who did reasonably well in top flight GP racing using an outboard motor re-purposed into a bike chassis beating the factory bikes. Lastly, possibly the award for most off the wall interpretation of any motor racing rules has to go to Smokey Yunick: https://en.wikipedia.org/wiki/Smokey_Yunick
Not quite the same pioneer as Britten but equally as adept at making do with what he had to hand:
Ken Warby - https://en.wikipedia.org/wiki/Ken_Warby
He's held the water speed record since the 70's in a boat built with hand tools on his driveway. Tried buying a jet engine from the US air force and they told him it was too secret so he bought an older one that had been scrapped and "rebuilt" it.
Didn't have any tools that could repair the damaged turbine blades or any that could even grind/shape them so he smashed the damaged blades out with a hammer and cold chisel then smashed the opposite blades to try and balance it up.
Then strapped himself into the thing and did 300 mph on water, plenty have tried to break it since but no one has managed.