The Spitfire PR. ID was a reconnaissance variant of the Spitfire. It was the first of the type to not be a conversion from older Mk. Is. It carried so much fuel that it was nicknamed as "the bowser", after a famous tanker lorry type of the era. The D-shaped wings housed the integral fuel tank and had an additional one in the rear fuselage. The type was also equipped with two vertically mounted F24 cameras in the rear fuselage.
The weight of both the cameras and the fuel, put the centre of gravity so far back that the type was difficult to fly until the rear fuselage tank was empty. In spite of those difficulties, the PR.ID proved to be worthy, reaching long distances and performing missions over Stettin, Marseille, Trondheim and Toulon.
After the first two Type Ds had proven the concept the production aircraft, which were soon renamed as PR. Mk. IV, the type was modified to increase the leading edge tank capacity to 66.5 gal (302L) and by deleting the rear fuselage tank. The PR. IV was equipped with the more powerful Merlin 45 engine, the same one employed by the Mk. V and had heated cabins, which came as a great confort for the pilots on such long flights.
On another related subject, the Spitfire fought against high-altitude bombers too. Near the end of August 1942, the Luftwaffe began a high-level bombing raids campaign against England. For such task, a new unit was created, called Höhenkampfkommando der Versuchsstelle für Höhenflüge (literally "High Altitude Combat Command of the High-Altitude Flight Test Centre) which was equipped with a small number of Junkers Ju.86R high altitude bombers. This aircraft was capable of bombing targets from above 40.000 ft (12.000 m), far outside the range of any Royal Air Force's (RAF) fighter ceiling, or even from anti-aircraft guns range. On one such attack, on 28th August a single bomb dropped over Bristol killed 48 people and injured another 46. To counter this new threat the "High Altitude Flight" was formed at RAF Northolt. This unit, equipped initially with a just a pair of Mk. Vcs which were soon converted into Mk. IXs by Rolls-Royce at the Hucknall plant, successfully intercepted a Ju.86R on 12th September over Southampton at 41.000 ft (12.000 m). The ensuing aerial battle, which went up to 43.000 ft (13.000 m), became the highest battle of the war. However, problems caused by the freezing air at that altitude, meant that the combat couldn't be decisive as the port cannon jammed and, every time the pilot fired a burst, the aircraft would slew and fall out of the sky.
The bomber escaped safely with just one hit to its port wing. However it was found to be vulnerable to the RAF at high altitudes and the Luftwaffe launched no further high-altitude attacks against England..
Sources:
1st https://en.wikipedia.org/wiki/Supermarine_Spitfire_(early_Merlin-powered_variants)
2nd https://en.wikipedia.org/wiki/Supermarine_Spitfire_operational_history













