We have a winner
Yes this is the ' Panthere' by the French sculptor Casimir Brau. The MG 18/100, of which only 5 were produced, was the only MG to be offered with an official mascot fitted. The 18/100 was unofficially known as the Tigress (even though the mascot was a panther!).
Due to its weight it was actually fitted to the headlight bar and not on the radiator cap, you can see it between the headlights in the photo of the car I posted above.
Cecil Kimber had one on his desk as too did George Tuck, the MG publicity manager.
The new Question
Name the cars