As per original design specs in good old mph terms:
Long Haul: CV 990 . High speed cruise worked out at 610 mph at 20,000ft , - Economical cruise 556 mph at 35,000 ft. (880 didnt have the streamlined wing fences and was about 10 mph slower).
ATC folk will well remember some of the sporty performances of the 990 around Europe when operating for Spantax
Short Haul: Trident 1 high speed cruise at 27,000 ft was 605 mph and economical 596 at 30,000. I seem to remember though BEA early on advertising it as a 610 mph aircraft, presumably rounded out upwards to the nearest 10mph.