This is a Notable Operational milestone.
The first flight was actually by the second prototype (-V2), which was equipped with the Bölkow semi-rigid main rotor. The first protoptype (-V1) flew with a Westland Scout main rotor and was destroyed in a ground resonance incident.
The protoypes had different engines,
V1 - Allison T63
V2 - Allison 250-C-18
V3 - MAN-Turbo 6022A3 (it first flew on 20 Dec, 1967)
V4 - TBA (it first flew 01 May, 1969)