You missed out on a fantastic opportunity there mate. If some mentally handicapped guy started on me like that, I'd really fancy my chances.
And once I'd started getting the better of him, I'd throw in a bit of Mohammed Ali footwork and maybe finish the monger off with a crane kick like on Karate Kid!!
Then those Pguys behind the counter would know who's boss.
#edit# or stop being a fanny 😆
*disclaimer* the language used above is for comic effect only, before the lentil brigade start complaining