Most postnominal letters - royal

HRH the Duke of Windsor (1894-1972) had 10 sets of post-nominal letters when he was Prince of Wales. These letters were KG, KT, KP, GCB, GCSI, GCMG, GCIE, GCVO, GBE, MC. As a privy counsellor, he also included PC after his name, and later appended the ISO but omitted OM, CH and DSO-orders of which he had also been sovereign.