Green’s Dictionary of Slang

(Aus.) an emphatic interjection: no problem! no fuss! no doubt about it!

1846		Swell’s Night Guide 51: It vas hout-and-hout good scoff, and no flies.
1859		H. Kingsley Recollections of G. Hamlyn (1891) 297: ‘Is so,’ says he, ‘and no flies.’.
1860		Era (London) 20 May 4/3: Mister Sim Smanks whistled and said that wore a game as he should like to see played out, and no flies.
1865		Leaves from Diary of Celebrated Burglar 37/1: As soon as all were seated, Tommy received the usual order to bring in half a dozen of his French best, and no ‘bloody flies’.
1882		Sydney Sl. Dict. (2 edn) 6: No Flies - Emphatic in the affirmative.
1887		‘’Arry on the Jubilee’ in Punch 25 June 305/1: Well, she won’t be ashamed of ’er subjeck, that’s poz, dear old pal, and no flies!
1890		Bulletin (Sydney) 23 Aug. 17/2: Well, to prove to you I am the better man, and no flies, I won’t reckon I’ve won this race; we’ll regard it as a dead-heat, and come out to-morrow or the day after and row off the decider?’.
1903		Truth (London) 18 June 1678/3: Slang terms: [...] fizzing, loud, nobby, no-flies, O.K., out-and-out, pick-me-up, pink, posted-up [etc] .
1914		Joyce ‘Grace’ Dubliners (1956) 161: ‘There’s no mistake about it,’ said Mr M’Coy, ‘if you want a thing done and no flies about, you go to a Jesuit.’.
2019		P. Baker Fabulosa 288/2: and no flies honestly!