I worked on Gazelles back in 1973 ShyTorque and by my calculation that was more than thirty years ago.
We also had some proper wobblycopters - good old Westland Whirlwinds powered by the Gnome - which, as all true wobblycopter magicians know, used a free power turbine. The twin-engined Wessex used a pair of Gnomes but wasn't that much more complicated than the single-engined Whirlwind - if one engine stopped, Hawker-Siddeley's wondrous Electronic Fuel Control System - a magical contraption that performed the tricky computations using magnetic amplifiers - sorted it all out and ran the remaining engine up to full power. If you were lucky...