1 is a name applied retrospectively to the first aircraft constructed by Geoffrey de Havilland, who built and flew it once in December 1909.
The resulting design was a three-bay biplane with an open-truss fuselage, equal-span unstaggered wings, and a four-wheeled undercarriage.
With construction continuing at Fulham, de Havilland and Hearle looked for a site to test the aircraft.
During a visit to Crux Easton in the summer, they discovered unused sheds that had been built on Lord Carnarvon's estate at Seven Barrows by John Moore-Brabazon.
By December, de Havilland and Hearle relocated the aircraft to the sheds and took rooms at a nearby inn.