What do you have under the hood?

I saw this monster at the Bo Peep Hill Climb, East Sussex, UK, last Sunday. Home built machine, with a significant engine - Rolls Royce Merlin, I believe top half Hurricane, lower half tank. It sounded as beautiful as it looked, especially starting up:
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The hill is only 600m or so long and steeper than Goodwood, but even so it drank just over a gallon to do one run!

See it off the line at 48:18!

https://www.youtube.com/watch?v=wuk-5IM7wAo

Mad as a box of frogs!