In nearly 3000 hrs of Wessex time I only had one engine run down on me and a spurious fire caption - other than that, the old girl just kept on going.
It was a top SH machine, hampered only by its lack of top speed and limited power due to the transmission layout. If you wanted to land a team of hooligans in some bad boys front garden at first light then the Wessex was the machine to do it in - that undercarriage saved my bacon (and embarrassment) on several occasions.
I think Lu is right, in that Westlands copied the combining gearbox so that the RR Gnome could be used (the same engines keeping me up in the air nowadays!).
Hot and high was a problem for the old girl - running out of TR authority at the top of Troodos was always entertaining.
A rattly, underpowered junk bucket by comparison to modern helos but in its day it truly was 'Queen of the Skies'.