It's actually the war banner of the Guelphs who were a medieval group of nobles who fought on behalf of the papal state.

The Guelph war banner (the red cross) can be found on the civic arms of traditionally Guelph towns like Milan, Vercelli, Alessandria, Padua, Reggio and Bologna.



Compare this to the Ghibellines (Holy Roman Empire) war banner which consisted of a white cross which can be found on the civic arms of traditionally Ghibelline towns such as Pavia, Novara, Como, Treviso and Asti.



============================================================================================

I also found this on Wikipedia,unfortunately i can't find the original source of the information.

In 1188 Henry II of England and Philip II of France agreed to go on a a crusade, and that Henry would use a white cross and Philip a red cross. 13th-century authorities are unanimous on the point that the English king adopted the white cross, and the French king the red one (and not vice versa as suggested by later use). It is not clear at what point the English exchanged the white cross for the red-on-white one.

en.wikipedia.org/wiki/Flag_of_England#Origins

All I can think of now is the red dwarf emohawk episode... 'This is GELF space...death to the strangers!' lol

Very entertaining program Red Dwarf



talking of morphing do forum members thing the Ghibellines eventually morphed into the Bavarian Illuminati ?

They share some similarities-

Made up of nobles and landed gentry.
Fought against agents of the pope.