1954 Lagonda DP115 V.12 with later Aston Martin DB3S-style grille
This is the right one!
I had it as about 1955 but '54 might well be correct..
They were built for Le Mans 1954 but proved disastrously useless. The one car that started crashed fairly early on - the driver was Eric Thompson who was very much a gentleman driver and probably too tactful to say what he thought of the car. A second car raced later in the year at the British GP meeting, but was slower than the 3-litre Astons. This must be the car, although my investigations prior to posting did not reveal which chassis is represented by the puzzle car.
The 1955 Lagondas were based on a completely new chassis, which was later used as the basis of the new DBR2 cars - which WERE successful tosay the least. The DP115 cars famously starred in the film "Checkpoint", a sort of Mille Miglia pastiche - hence the changing of grilles and later reversion to an "Aston" style. (In the film , the rival "Ermini" team was the old Fairthorpe factory).