YY4 was campaigned extensively by A W F Smith in the thirties. Chassis number J2714. It appeared at an auction in East Sussex in the early 70s in very original condition and sold for quite a nominal sum - can't remember exactly how much but even I could have afforded it.
As Colin says YY4 is a very well documented car with extensive pre war trial history and in many pre war photos. It is very original and was for sale at a very reasonable price at MG Silverstone about 8 years ago - wish I had purchased it ! Not sure where it is now. JF 5278 is Gil Collins much campaigned blown swept wing J2 - a very quick car.
A. W. F. Smith had a dry cleaning business in either Norfolk or Suffolk, and trialled very successfully from 1932 to 1937. He did the Brighton Run in a 1903 Clement in 1936, and owned Tamplins in the 1950s