The event was named after Dudley Benjafield, one of the famous Bentley Boy racers and a winner of the French race in 1927. According to Goodwood Road and Racing, 21 prewar cars entered, and astonishingly, 20 finished. Teams of three or four drivers did two-hour shifts, and more than just old Bentley racers competed. Robbert Alblas, who also made the awesome video above, told Autoblog via email, "The organization is not a allowed to call it a race because of insurance reasons." Therefore, there were no official rankings of where the competitors actually finished. That's a pity, but it doesn't take away from how awesome an undertaking this was.
While you can see cars from this period briefly racing at events like the Monterey Motorsports Reunion, witnessing them go for 24 hours is almost an impossibility today. Check out Alblas' fantastic short film of the Benjafield's 24, above, and get a taste of the on-track action.