From Longman Dictionary of Contemporary Englishand no mistakeand no mistakeBritish English spoken informalCERTAINLY/DEFINITELY used to emphasize the description you have just given Miles was a heartbreaker, and no mistake! → mistake
Examples from the Corpus
and no mistake• They looked like barmen and no mistake.• My word, it's a bad business and no mistake.• It was a Cinderella dress and no mistake.• It was a real kettle of fish and no mistake.• But there was no fluke, and no mistake, about what happened here Sunday.• She was a lively one and no mistake.• A good sort and no mistake. 