Although only five Irises were built, it was used as a long-range maritime reconnaissance aircraft by the Royal Air Force, where it equipped a squadron for four years, being used to carry out a number of notable long-distance flights.

[3][4] The prototype R.B.1, with the designation Iris I, and with the serial number N185, made its maiden flight from Blackburn's factory at Brough on 19 June 1926, being delivered to the Marine Aircraft Experimental Establishment at Felixstowe the next day, being fully tested during July and August.

N185 returned to Brough in March 1927 when it was fitted with the new metal hull, together with more powerful engines and an additional gunner's position in the tail, becoming the Iris II.

It reached Karachi on 14 October, finally returning to RAF Calshot on 14 November, having flown a total distance of 11,360 mi (18,290 km) with a flight time of 125 hr 5 min.

[11] The first Iris III was destroyed in a fatal crash on 4 February 1931, killing nine of twelve aboard, when the pilot misjudged a landing approach over a glassy-smooth Plymouth Sound.

[17][18] One of the Iris Vs was converted for use as a testbed for the Napier Culverin, a licence-built Junkers Jumo 204 diesel engine, flying in this form in June 1937 and continuing flight trials until April 1938.