The Merlin XX has four valves per cylinder and a two speed supercharger. Mr. Hares' model has all of that and the link has a video if it running on a test stand. Seven thousand parts and six thousand hours. Mr. Hares also has built a Rolls-Royce Eagle 22, this is a twenty-four cylinder "H" block engine.
Here is a Wiki page for the Rolls-Royce Merlin series:
It runs, the gearbox shifts, the clutch clutches and the brakes brake. There are actually two of them! He also has a 1/3rd scale 330 P4 complete and the engine for a 250GTO is complete and here's hoping for the complete car someday