From Wikipedia ....
"Until the early 1930s, squadrons and units would use their own informal badges and insignia. In 1935, the process of formalising the badges was undertaken whereby an official heraldic approval would be granted by the ruling monarch of the time. The whole design process would ultimately rest with the Chester Herald as the Inspector of RAF Badges. This has changed over the years and has been filled by Clarenceux King of Arms and by the Surrey Herald of Arms Extraordinary. The Inspector of RAF Badges would liaise with squadrons and units to finalise designs that would reflect already adopted insignia or to utilise something suitable to recognise the squadron or unit. An Air Ministry Order (A.8/1936) was issued in January 1936 and detailed the criteria for badges and their ultimate approval via the Chester Herald and the king. In June of the same year, King Edward VIII approved the first raft of badges for numbers 4, 15, 18, 19, 22, 33, 201, 207, 216 and 604 Squadrons.
.... Flying squadrons were additionally expected to display their badge (or the main insignia/blazon from it) on their aircraft. This was also to be enhanced by the addition of a white shape behind the badge or insignia that would aid in seeing the badge and the particular shape would denote the role of the squadron; either a fighter, bomber or reconnaissance squadron, though some doubled up on their role. Non-flying units would display their badge on a sign either at the entrance to the base or outside the station headquarters."
The background shapes as adorned on Royal Air Force aircraft to denote the type of role operated by that particular squadron;
A) Fighter/Fighter Reconnaissance,
B) Bomber/Torpedo Bomber,
C) General Reconnaissance/Army Co-operation
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Regarding the pics you posted above,
The Gladiator is of no. 80 Squadron RAF. The badge of the unit was the "Bell" and therefore the fin emblem is with the yellow one at the A background shape type that was used for the fighter squadrons. The badge is in commemoration of one of No. 80 Squadrons early commanders, Maj. V.D. Bell.
The Spitfire is of no 72 Squadron RAF . The badge was the 'Swallow" intended to symbolise speed.
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All the RAF badges also called the RAF crests started being adopted in the WW1.