04/30/2009. Remarks by Johan Visschedijk: "In March 1934, K3503, the fifteenth and last Heyford Mk.I, was retained by Handley Page at Radlett as a trials aircraft for speed increasing features, including enclosed cockpit, improved front gunner position, refined nacelle/wing junctions, and more powerful engines. It was fitted with two 640 hp Rolls-Royce Kestrel VI engines and flew for the first time in June 1934. It is pictured here with the RAF Hendon Air Display 1934 catalog number '14' on the front fuselage."