The HCC12s were the jet propelled Whirlwinds built for the Royal Flight; one lost it's rotor assembly in December 1967. There were, however, two predecessors that became Whirlwind 10s. They were XN126/7 that started off as VIP Whirlwind 4s and were then upgraded to 10s when Aunty Betty got her new ones.
We had XN126 on 230 Sqn.; you could tell by the shiny steel grab handles under the paint.
Interestingly as Phil is in the news there was severe consternation when XR487 crashed. The Duke was in Germany with XR486 and apparently he should have been in 487.
XR 487 had gone U/S for something so XR 486 was substituted.