It's worth explaining about how the RAF started it's journey into photographic reconnaissance at this period of time. I will only cover this area very loosely, there are a number of very good books and even websites that go into greater detail about this subject. The idea is to show you that at the out-break of World War, the British military had a very young and maturing photographic reconnaissance capability

Because of the lack of photographic reconnaissance during the build up to War and the fact that the RAF's dislike of specialist Units and men, the Secret Intelligence Service (MI6) working with the French commissioned the Australian Sidney Cotton to fly clandestine photographic surveillance missions using Cotton's Aircraft Operating Company based at Heston airfield.

A picture of Sidney Cotton taken in 1941 and one of his Lockheed 12A that was used to fly covert reconnaissance sorties over Europe and even Berlin before the start of the War.

Flying Officer Bob Niven joined Cotton in early 1939 to act as his co-pilot and flight engineer.  Cotton first had fitted to the Lockheed, 3 Leica cameras, 1 in the vertical position and the other 2 at an angle each side. However, it was found that the picture format was to small for the detail required when flying at 20,000 feet, so these were replaced with the standard RAF camera at the time, the F24. The pair were mounted in a frame and set so that each camera's imagery overlapped, thus from 21,000 feet they could almost cover a 11 mile wide strip. Also the cameras were light enough so after completing a sortie, they could be removed and carried in a suitcase pass any customs officers. From the outside the camera port holes were covered by panels, thus making them almost impossible to see.
Sidney Cotton's Company was formally taken over by the RAF in September 1939, the secret Flight at Heston became No.2 Camouflage Unit. Cotton was given a commissioned rank of Squadron Leader with the action rank of Wing Commander. He then went on to fight for the best he could obtain from the Air Ministry in both equipment and men. In a period of 12 months, Cotton revolutionised the role of photographic reconnaissance in the RAF. Sadly, the Air Ministry in their minds could see that Cotton's Unit was becoming his own private airforce, 'Cotton's Circus' it has been called, so on the 16th June 1940 Cotton was handed a letter stating that he had been dismissed as Officer Commanding of the Unit and it was being placed under the command of Commander-in-Chief Coastal Commander with Wing Commander G W Tuttle appointed has the new CO.

Goto RAF Photo Reconnaissance Units to see how Cotton's reconnaissance dream developed

If it had not been for Sidney Cotton and his ideas the Royal Air Force's ability to obtain any form of aerial intelligence would have been found to be wanting.  Prior to Cotton tactical photo-reconnaissance for the Army was in the hands of Squadrons of  Lysanders, with long-range strategic reconnaissance being undertaken by a number of Squadrons of Blenheim IV bombers of No. 2 Group.

An example of a Lysander.

On the right is a drawing showing very basically the role of the Blenheim flying in the reconnaissance role. On an operational sorties, reconnaissance aircraft would not have flown in pairs.
Both these types of aircraft were slow and because of the heights they had to flight to obtain the best imagery, they became easy targets for the Luftwaffe.
The first operational sortie of the War was undertaken by a photographic reconnaissance Blenheim of 139 Squadron from RAF Wyton. However, flying at 24,000 feet froze the camera and the aircrafts radio and it returned to base.

The PR Mk IA was the mark of the first two Spitfires converted for photographic reconnaissance for RAF service, they were handed over to the Heston Flight on the 30th Oct 1939. Two F24 5in focal length cameras were placed in the wings in place of the guns, both were mounted in the vertical position. One of these aircraft became the first Spitfire to operate overseas when it joined the British Forces in France in November 1939, flying the first reconnaissance sortie on the 8th of that month over Aachen (the weather prevented her pilot from taking any useful pictures). The two PR Mk IA's were later converted to the PR Mk IC standard.

The PR Mk IB was an up-grade to the PR Mk IA. The cameras were fitted with newer 8inch focal length lenses. Also, an extra 29 gallon fuel tank was installed behind the pilot. This version was first used on 10 February 1940 when it took photographs of the German naval bases at Wilhelmshaven and Emden.

PR Mk IC entered service in March 1940 and was the first PR mark to be produced in large numbers. In all a total forty were produced by up-grading other aircraft. A 30 gallon fuel tank was added under the port wing, thus increasing the range, this also helped to balance the two F24 cameras (each fitted with 8in focal length lenses) that were placed in another blister under the starboard wing. It could also have fitted a F24 in a vertical position in the rear fuselage behind the pilot.

The blisters can clearly be seen in the  image below of a Mk IC in flight. In the top left image, ground crews can be seen working around the aircraft and the camera blister can just be seen in the open position. The bottom image shows the 2 F24 cameras mounted within the blister.

The PR Mk ID (PR Mk IV) was produced as a super long range version, both wing leading edges were fitted with 66 gallon fuel tanks and the total fuel load including the 30 gallons behind the pilot was 218 gallons, giving it the nickname 'the bowser'. The camera installation was of 2 F8 20in focal length cameras or 2 F24 14in cameras mount again behind the pilot. The cameras could be inclined so they would produce overlapping imagery.

Only one PR Mk IE (PR Mk V) Spitfire was produced for low-level photography reconnaissance, it represent a significant development in that it was the first PR Spitfire to be equipped with an oblique camera. It had an F24 camera installed under each wing in a bulged fairing with the lenses at right-angles to the line of flight and looking slightly below the level of the horizon.

The PR Mk IF (PR Mk VI) was produced to fill a gap before the appearance of the PR Mk ID. It had two extra 30 gallon fuel tanks below the wings as well as an extra fuselage tank, giving it an endurance of four and a half hours, putting Berlin within range . The PR Mk VI started appearing in March 1940, seven months before the Mk IV. It carried two F24's with an 8in focal length, which were later replaced by two F8's with a 20in focal length. Finally, some PR Mk IF were given a F24 with a 14in focal length in an oblique mounting. The image is of a PR Mk IF that operated in Canada. This aircraft was used to photograph an eclipse of the sun in July 1945.

Undertaking low level oblique reconnaissance sorties put the PR Spitfire into the range of German fighters. One response was to produce an armed PR Spitfire. The PR Mk IG (PR MK VII) carried the standard machine guns of the Mk Ia, combined with the extra fuselage fuel tank of the PR versions. It carried one obliquely mounted F24 camera with a 14in focal length, which could face to the left or right, and two vertically mounted F24 cameras, one 5 inch and other with a 14 inch focal length lens. A total of 45 PR Mk IG's were produced by converting the standard Mk Vs.

The PR Mk IX first started to appear in November 1942, this version was a slight improvement on the pervious mark. But they were only a stop-gap for PR Mk XI. In total only 15 PR IXs converted from the fighter Mk IX versions at RAF Benson. For long-range missions they had to have a 'slipper' tank added under the fuselage, as they were not fitted with internal wing tanks.

The PR Mk X appeared in Spring 1944 (long after the PR Mk XI). It was the PR version of the standard Mk VII fighter, produced by matching the fuselage from a Mk VII with the wings from the PR Mk XI, with the guns replaced by two 66 gallon fuel tanks. Only sixteen were produced, and it was withdrawn in September 1945.

The PR Mk XI was produced in greater numbers than any other PR variant, with over 470 produced in total. It was based on the Mk IX fuselage, but with the extra fuel tanks of the standard PR variants as well as wing mounted tanks. It entered service in the summer of 1943. The PR Mk XI used a universal camera installation, which allowed the cameras to be easily changed. This allowed a much wider variety of cameras to be used and as such it could undertake a great range of tasking. Common variants included two F52 cameras with a 36in focal length lens, two F8s 20in focal length lens , one F52 20in focal length and two F24 14in focal length lenses combined with one F24 with either a 14in or 8in focal length lens fitted in an oblique position. Some also carried a 5 inch focal length F24 just behind the wheel well for low to medium level tactical reconnaissance.

The bottom image is a PR Mk XI of the USAAF.

Click image for an enlargement

The PR Mk XIII was a low level reconnaissance fighter, converted from old Mk I, Mk V and PR Mk VII. It carried four machine guns for defensive armament, which somewhat limited its range. It went into service in 1943. PR Mk XIIIs were amongst the aircraft used to take low level pictures of the Normandy beaches in preparation for the D-Day invasions. It carried two vertical F24 25in focal length cameras and one oblique F24 5in focal length camera.

The PR Mk XIX was the only Griffon powered reconnaissance Spitfire. It was produced by taking the Mk XIV fuselage, adding the PR Mk XI wings and PR Mk X cabin. It could carry 254 gallons of fuel internally, using space in the wings that had originally held cameras. It could also carry a 170 gallon drop tank, although this was limited to 90 gallons on operations. It had a top speed of 445 mph and a service ceiling of over 42,000 feet, putting it out of the range of Luftwaffe. All but the first 22 of the 225 produced were equipped with a  pressurised cockpit. The PR XIX could carry two vertical and one port side oblique camera, the vertical cameras were either F8s with a 14 or 20in focal length or F52s with a 20in focal length. The oblique camera was an F24 with either an 8 or 14 inch focal length. It entered service in May 1944. The last operation flight by an RAF Spitfire was made by a PR XIX on 1 April 1954. Three continued to fly with the Temperature and Humidity Flight, performing meteorological research, until they were finally retired on 10 June 1957.

Spitfire PR XI and 2 PR XIX at RAF Benson 1945
In the background more Photo Reconnaissance Spitfires and Mustangs can just be seen.