Chris VMO on the Trident was 365 knots.
The Trident 1s were reengined as it couldn't get airborne from Heathrow with a full load in summer...hence the nickname "gripper". (Ground gripper...got airborne due to the curvature of the earth).
Whilst the Trident did set records...some courtesy of pulling a certain circuit breaker as the overspeed siren would give one a headache..
The VC 10 also set a subsonic trans Atlantic record which stands today.
Biggest problem with the Trident was the way we flew it because many "couldn't".
The Iron Duck was a different kettle of fish and a real gentlemans aircraft.