Gwenda Stewart (nee Hawkes) with the Derby-Miller front wheel drive racing car. Like other marques of the period, Derby involved themselves in motor sport, with driver Douglas Hawkes's front wheel drive Miller with Derby parts (dubbed a Derby-Miller) acting as a testbed and promotional tool; that it was driven by Gwenda Stewart did not hurt publicity either. He had bought into the Derby factory in 1930, helped by his then father-in-law Charles Kinisson.
Although Stewart had been known to say that she preferred record-breaking to racing as it required less effort, she was nevertheless a quick and skillful racer; she raced at Montlhéry, taking a Land Speed Racing 1.5 litre class record at in 1930, with a standing mile at 118.13mph. She also raced at Brooklands, and twice at the Le Mans 24 Hours, in 1934 and 1935. She was partnered by Louis Bonne and Charles Worth respectively, but retired early both times.