I managed to buy the original photograph in the puzzle picture on sunday, and have been inspired by that to do a little more digging.
Lt. Dick Staddon was a director of Ransomes, Sims & Jefferies, the agricultural engineering firm, makers of tractors, mowers etc. He competed pre- and post-war in a Lancia Lambda and later Bugatti Type 37. He sold the Bugatti to fund the construction of this car.
The initial construction was done by V W Derrington, the well-known tuning firm in Kingston. As previously stated, the car was fist built with skimpy cycle wings and later changed by 'a second firm' into the modernised car seen here. According to an advert by V W Derrington in November, 1950, the car has a 'Lester body' so presumably it was Lester who made these wings. I have never heard of Lester building bodywork for cars other than his own, however.
Staddon obviously didn't keep the car very long if it was built in 1949/50 (earliest reference I can find is August, 1950, and the car is already wearing the later wings). It was still for sale in January, 1951, after which I'm not sure what happened to it. I don't know if the car was a genuine attempt to go into production, but in the 1980s Mike Wilsdon had two chassis, three bodies and enough component parts to complete two cars (including the original cycle wings) so at least that many were started if not completed.
The name TDC is how Wilsdon referred to the cars, but in period material it is only ever referred to as a Derrington-Fiat or Staddon-Fiat.
Mike's collection was broken up some years ago and I have no idea what became of the TDC/Staddon/Derrington-Fiats. I think he is still around and in London and I would like to get in touch with him to discuss this and other cars, if anyone knows how he might be reached let me know.