Having looked at the Jensen Genome, chassis 541/465206 was registered as WUB 1, November 1955, deep carriage green, with red trim. Straight forward 541.
A 541R was also registered as WUB 1 in August 1959 , also deep carriage green and red interior. Chassis 3946002 so I reckon it’s got to be the car in the photos.
Chassis S1092/100 Indigo Blue, red interior, was registered WUB 1, in November 1961 and would be the car my friend John owned.
It does seem totally plausible that the driver, “S H Burton” would have been Stanley Howard Burton, born 1914, a son of Montague Burton, founder of Burton’s tailors. He clearly had the means to buy, run and race a number of 541 cars!