Thanks MG - that's how I remembered it
Actually in order to reduce drag the exhausts were modified to face aft, it was realised that by reducing the duct area a small amount of residual thrust was gained, because the exhaust was a by product of the powerplant supplying the thrust generator itself (the rotor) and had to be gotten rid of it is not considered as thrust compounding which is why it is the helicopter record not a rotorcraft one and why the claims for the X2 are spurious, that is a true compound.
The bonus of The thrust on G-LYNX was a happy accident