I looked further into the Bruce-Brown story and discovered unresolved controversy regarding his age, which could have been either 19, 20 or 22.
- Peter Helck (1961 and again 1983) wrote that Bruce-Brown was 24, when he died on 1 October 1912. This means he was born before October 1888 and at the time of his first American Grand Prize win on 12 November 1910, he was actually 22.
- G N Georgano & Cyril Posthumus (1971) show him to be born in 1890, which makes him either 19 or 20 at the time of his first American Grand Prize win.
- Robert Cutter and Bob Fendell (1973) wrote that he was born 1890 and refer to him as 18-year-old on March 23 1908, when he set a record speed of 109 mph at Daytona. Conclusion, he must have been born before March 23 1890. That makes him 20 at the time of his first American Grand Prize win.
- Tim Considine (1997) states that he was born 1890, which would make him either 19 or 20 at the time of his first American Grand Prize win.
I believe that David Bruce-Brown was the youngest ever to win a major event.