[Edited to include additional details.]
I believe this is the HWM/Alta-Jaguar that Phil Scragg constructed using the first Alta grand prix chassis, "GP101." Frank Brown imported the car to Uganda in 1959 (where it acquired registration "KHJ 144") and then to Kenya. It was later owned and raced by Peter Shepherd, Peter Sargeantson and Beau Younghusband before returning to the UK.