If my aged brain is still remembering things aright the CT&/T700 was chosen because the DGA(N) at the start of the WG34-EHI-Merlin saga ( was it rocket Ron Holley?) still bore the scars of the Lynx development and vowed that there would never be another new helo engine developed in a new airframe on his watch.
Rolls then managed qualify and demonstrate the RTM 322 for the US Seahawk/Blackhawk so it could be deemed not to be a new engine. By then most of the PP's were flying on T700's anyway.
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