The Anson was derived from the commercial six-seat 652 model; the militarised version, which first flew on 24 March 1935. The aircraft was built to Air Ministry Specification 18/35. It was the first RAF monoplane with a retractable undercarriage. Avro allotted the type number 652A to the Anson. The first production run resulted in 174 Mk I aircraft for service with Coastal Command. No. 48 Squadron RAF was the first to be equipped in March 1936. A total of 11,020 Ansons were built by the end of production in 1952, making it the second-most-numerous (after the Vickers Wellington), British multi-engined aircraft of the war.