From: Cierva Autogiros by Peter W. Brooks:
“Cierva C.30A Rota seaplane. (140 hp Armstrong Siddeley Civet 1). Following test-flying by Cierva and Marsh from the River Medway at Rochester between April 13 and 26, 1935, Marsh ferried the Rota seaplane (K4296) mounted on Short F.60 type twin floats from Rochester to Felixstowe. At Felixstowe, this aircraft was tested for the Air Ministry at the Marine Aircraft Experimental Establishment. During these tests, Marsh had a most unpleasant experience. On the evening of April 29 he started a test dive at about 6,000 ft (1500 m) and at 110-115 mph (188-185 km/hr) suddenly experienced a violent nose-down pitching moment that he was unable to arrest with the control column. The machine bunted onto its back and Marsh found himself flying upside-down at 3,000 ft (900 m) with the rotor below him. At this point some lead ballast in the front cockpit fell out of the aircraft, fortunately missing the revolving blades as it passed through the rotor disc. The machine then righted itself of its own accord and Marsh, who had meanwhile switched off the engine, force-landed on the open sea immediately beneath. He climbed onto a float, swung the propeller, and taxied back to Filixstowe. An eyewitness recorded that Marsh’s only comment when he reached the slipway after this ordeal was “When’s the next blankety-blank train back to London?”