In March 1938, a photographic interpretation cell, AI1(h), was formed at the Air Ministry under Squadron Leader W H G Heath. Bomber Command of the RAF later formed a photographic interpretation section, commanded by Squadron Leader P J A Riddell and manned by graduates of the Army Interpretation Course at Farnborough. Meanwhile, F S Cotton, a freelance aerial photographer, had been conducting clandestine photographic flights over Germany in his private aircraft.
On the outbreak of war in September 1939, a small photographic interpretation section was attached to the Intelligence Staff of the Headquarters British Expeditionary Force (B.E.F.) - GSIa(V), which consisted of three officers trained on the Army Interpretation Course. The Royal Air Force reconnaissance aircraft - the Bristol Blenheim - was soon found to be inadequate for its long range photographic reconnaissance role and trouble was also experienced with existing camera systems. The only source of long range aerial photography was Cotton in his personal Lockheed. Cotton persuaded the Air Ministry to give him an assortment of Hudsons, Beechcrafts, Blenheims and even Spitfires for adaptation as photographic reconnaissance aircraft. This small group of aircraft operated from RAF Heston, Middlesex, on secret reconnaissance operations and was officially known as No 2 Camouflage Unit. Wing Commander Cotton commanded the unit, later known as the Special Flight, and experimented with modified, unarmed Spitfires, flying at heights above 30,000 feet.
Cotton sought the aid of his friend Major H Hemming, Managing Director of the Aircraft Operating Company Ltd, an aerial survey firm at Wembley. The Heston Special Flight, which was renamed the Photographic Development Unit (PDU) in January 1940, continued, unofficially, to use the resources of this company to process and interpret its films and to make detailed drawings with its special equipment. Finally, after much pressure from the Admiralty, the Air Ministry decided to give the Company a formal contract to operate as part of PDU from 1 April and later that month moved AI1(h) into the Company's premises at Wembley. AI1(h) merged with the Company in May and on 12 June 1940 the Wembley organisation was given its own identity as the Photographic Development Unit - Interpretation and Intelligence, (PDUI). Major Hemming, now in the honorary rank of Squadron Leader, was placed in charge of the section where he was joined by Squadron Leader Riddell from Bomber Command.
On 18 June control of PDU and PDUI passed from the Director of Intelligence, Air Ministry, to HQ Coastal Command and on 11 July a further renaming of the two units took place. PDU was renamed the Photographic Reconnaissance Unit (PRU), and PDUI became the Photographic interpretation Unit (PIU)
During 1940 the accommodation at Wembley was rapidly outgrown and the work was continually disrupted by bombing raids. In April 1941 PIU moved to Danesfield House, Medmenham, and was renamed the Central Interpretation Unit (CIU).
Later that year the Bomber Command Damage Assessment Section was absorbed, and amalgamation was completed when the Night Photographic Interpretation Section of No 3 PRU, Oakington, was integrated with CIU in February 1942.
During 1942 and 1943 the CIU gradually expanded and was concerned in the planning stages of practically every operation of the war, and in every aspect of intelligence. In 1945 daily intake of material averaged 25,000 negatives and 60,000 prints. By 'VE' day the print library, which documented and stored world-wide cover, held 5,000,000 prints from which 40,000 reports had been produced.
American personnel had for some time formed an increasing part of the CIU and on 1 May 1944 this was finally recognised by changing the title of the unit to the Allied Central Interpretation Unit (ACIU). There were then over 1700 personnel on the unit's strength. The title of the unit reverted to Central interpretation Unit when the Americans returned home in August 1945.
Early in 1945 a number of Photographic Interpreters (PIs) were sent to join the British Bombing Research Mission in Paris to explore the degree of damage and production interruption caused by Allied bombing in the Resistance areas of the Central Massif and in the ports. They were also tasked with checking PI reports which would eventually be related to assessment reports of attacks on German industry. Several PIs were also seconded to the Pentagon in Washington DC to join a detachment of RAF and Army Officers.
With the cessation of hostilities in Europe in May 1945 some sections closed almost immediately, whilst others worked on tasks for the Control Commission in Germany. The several Army sections of CIU were incorporated in September 1946 to become the Army Photographic Interpretation Centre (UK) (APIC (UK)).
The CIU was placed under the control of the newly established Central Photographic Establishment of Coastal Command which had replaced the disbanded 106 Group and the Joint Photographic Reconnaissance Committee (JPRC). In August 1947 the unit's name was changed yet again, this time to the Joint Air Photographic Intelligence Centre (UK) - (JAPIC (U)). In October 1947, APIC (UK) was renamed the Army Photographic Interpretation Unit (UK), (APIU (UK)), and although it continued to operate within JAPIC (UK), had special responsibilities to the Director of Military Intelligence. The Officer Commanding APIU (UK) was also deputy commandant of JAPIC (UK).
In March 1950 the Central Photographic Establishment was disbanded and administrative control of JAPIC (UK) was transferred to HQ No 3 Group, Bomber Command, with Intelligence Control exercised by the Air Ministry.
During 1951 the US Forces in Korea requested the assistance of RAF Photographic Interpreters and a detachment of PIs and Plotters was assigned to the 67th Reconnaissance Technical Wing based at Kimpo, near Seoul, in South Korea. Although the original request was for one detachment, this became a regular committment and many JAPIC (UK) teams saw service in Korea during 1951, 1952 and 1953.
In December 1953, the unit was given the title of the Joint Air Reconnaissance Intelligence Centre (United Kingdom), (JARIC (UK). The personnel of APIU (UK) were absorbed into the establishment of the Joint Service Unit and the Army has continued to provide a number of PIs and supporting staffs in the JARIC establishment.