Avro Anson, part Twelve, British users part one

Back in 1933 the British Air Ministry proposed the Royal Air Force (RAF) to acquire a cheap landplane for coastal maritime reconnaissance role, supplementing this way the more capable, albeit more expensive, flying boats. The Air Ministry requested designs from every major aircraft manufacturers to produce an aircraft suitable aircraft to meet this requirement. Avro answered the requirement with the Avro 652A which was a modification of the earlier Avro 652. After submitting the designs, the Air Ministry evaluated them and decided to place orders for single examples of the Avro 652A and the De Havilland DH.89 for evaluation purposes to meet this requirement in late 1934. The evaluation and the selection of the design was expected to take place during May 1935.
On 24th March 1935 the Avro 652A made its maiden flight at Woodford aerodrome, in Greater Manchester and between 11th and 17th May 1935 it competed against the DH.89 by the RAF's Coastal Defence Development Unit at RAF Gosport, in Hampshire. During these trials, the Avro proved to be superior and was selected as the winner of the competition on 25th May. Given its selection, the Air Ministry Specification 18/35 was written around the Avro 652A and shortly later an initial order for 174 aircraft which were given the name "Anson".
On 31st December 1935 the first production Anson rolled out from the factory. It differed from the prototype in having an enlarged horizontal tailplane and reduced elevator span to make stability better. Additionally, whilst the prototype wasn't fitted with flaps, production aircraft could fit their installation from the onset to increase the viable glide angle in order to reduce landing speed. On 6th March 1936 deliveries to the RAF begun. A total of 11.020 Anson were manufactured when the type ceased to be manufactured in 1952, making it the second most manufactured British multi-engined aircraft of the World War 2, only surpassed by the Vickers Wellington.

Sources:
1. https://en.wikipedia.org/wiki/Avro_Anson
2. https://www.valka.cz/Avro-Anson-t54872 (translated)
3. Hall Park Books - Warpaint 53 - Avro Anson