Gwynne-powered GN of H.S. Eaton, at Essex Meeting, October 1924.
Technical details:
"[Eaton] drove his GN successfully in sprint events. For the Track he put a Gwynne Eight engine into the GN, after this 950 cc push-rod ohv power unit had been highly tuned by Laystall's, and was claimed to reach 6,000 rpm. The driver's seat was arranged over the GN back axle. Gordon England made the body, which was a thoroughly streamlined single seater with cowled radiator and valance. The car made its debut at the 1924 Bexhill-on-Sea Speed Trials and ran that year at South Harting hill-climb when it broke a valve spring."
[Edited for clarification and additional details]