There is only one letter P, which is the individual letter of the aircraft. It could belong to any squadron. Only if you have a serial number could you find out the squadron or squadrons it belonged to.

By the middle of 1942 it was realised that the use of squadron codes was an aid to German intelligence in working out the order of battle of the RAF. It was proposed to stop using them and the various commands were invited to give reasons if they wished to continue using them. In December 1942 all RAF commands, including overseas, with the exception of Fighter Command and Bomber Command were ordered to stop using squadron codes. A little later Coastal Command started to use a numeral, 1, 2, etc, to indicate squadrons where there were two or more squadrons based at the same airfield. The numeral and individual letter were always separated by the roundel. When the first strike wings were formed Coastal Command petitioned to use squadron codes again as they now had aircraft from different airfields operating together. Their request was granted and squadron codes came into use again. Sometimes squadrons used their previous codes, in other cases they were given new ones.