This car was on loan at the Donington Park museum when I paid my last visit there in September 2014.
It's a 1929 Alfa Romeo 6C Sport Tourer, and the board at the side gives a brief history of the car as shown below:
Following the closure of the museum and the return of the car to the family it seems that it was put up for auction with Bonhams who gave a much fuller history of the car.
