Green’s Dictionary of Slang

no doubt (about).

1968		A. Buzo Norm and Ahmed (1973) 15: He’s a real cluey bloke, no risk.
1973		J. Powers Last of Knucklemen (1974) 63: Anyone working in this dump is nuts. Gotta be. No risk [AND].
1979		B. Humphries Bazza Comes into his Own [play script] The game was nearly up for Australia, no risk [AND].