Once worked with a bloke who impersonated an army officer. When I first met him he 'was' a CMF Major. I'd just come out of the army and he had all the correct gongs, uniform etc., but some of the stories & chronology didn't quite fit.
Had a promotion and organised the Anzac Day parade at Parramatta RSL, but shortly afterwards was convicted of impersonating a LtCol & fined, apparently on the suspicions of a couple of regular army Captains. (My suspicion is that a couple of the WW II blokes we worked with dobbed him in.)
Twenty years later, he had divided a small country town RSL. He now claimed to be a retired Brigadier. Half the club believed him, the other half didn't. It should have been easy to prove that he wasn' what he claimed to be, but he presented as extremely credible.