Green’s Dictionary of Slang

and no flies phr.

[the image is of flies settling on something that is fig. ‘off’]

a general intensifier, meaning ‘and no doubt or hesitation about it’.

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[UK]H. Kingsley Recollections of G. Hamlyn (1891) 297: ‘Is so,’ says he, ‘and no flies.’.
[UK] ‘Funny He-She Ladies!’ in C. Hindley Curiosities of Street Lit. (1871) 157: They would suck old nick in and no flys.