That's Gordon Parker's Jaguette special.
In the 1940s Gordon Parker combined an MG Magnette chassis and a 2½ litre SS engine to make this hillclimb special and combined the makers names to name the car "Jaguette"
The tyres look a bit big for this to be a photo of the car as built, so I don't know who the driver might be unless it's William Coleman who drove the car at Brighton in 1952.