Due to the wind, the WWI aircraft at the airshow couldn't be flown. But the guys were good enough to run the engine of the Sopwith Triplane.

This is a 130hp Clerget 9B nine cylinder rotary engine. The difference between a radial engine and a rotary engine is that whereas a radial engine is 'fixed', the rotary engine spins with the propeller as can be seen in this photo.

The reason for this is that early engines were notoriously unreliable. They had to have a flywheel in order to run smoothly, but on aircraft a large flywheel would've meant a heavier engine. A heavier engine would mean more power, more power would mean a bigger engine, meaning a bigger flywheel, meaning more weight... A never-ending circle. So instead the designers decided to make the whole engine into a flywheel to solve the problem!! Unfortunately this also meant that the engine RPM had to be carefully monitored and there were increased gyroscopic forces on the airframe (which became a killer on aircraft like the Sopwith Camel).

Photo taken at the June '11 Shuttleworth Airshow