I haven't been able to find a web page describing this car as a "Silver Flash". I thought only the Docker Daimler carried that name. Not sure about the 1953 part either.
Here are more images of the puzzle car. Daimler DK 400 All-weather Saloon by Hooper, Body No.10235, Engine No. 92716, formerly belonging to the Nawab of Bahawalpur.