MoS funded Bristol in April,1947(!; prototype build ITP, 1950) for a 10-seater, T.173, cut-and-shut from 2xT.171 (Sycamore, Leonides) power trains. RN had explored rotors for ASW since Cierva Autogiro, then Sikorsky R-4 Hoverfly; with MSP-$ RN in 1951 was assigned Gannet AS.1 for real carriers, wooden Short Seamew for escort carriers, and 18 Bell HSL-1 on other sterns. That type failed, so in 1954 T.191(Napier Gazelle) was funded for RN, T.192 for RAF, T.193 for RCN and T.194 civil variant. RCN soon fled to Piaseki, RN and the tiny civil market to (W)S.58. T.192 continued for RAF's Task of brown job insertion. In 1957, despairing it would ever emerge, MoS explored Fairey Rotodyne and DHC-4 Caribou, but chose to persevere with T.192 to give Bristol/Weston something to parlay in the industrial "coalescence" discussions. Bristol Aircraft and GW went to EE/Vickers, 18/12/59: MoA had hoped rotors too, but that went by default to WHL, 23/3/60. The 3 DB T.192 arrived in October,1960; WHL made no fuss about confining production to merely 26 and secured commonality RAF/RN with (GE T.58, as BSEL) Twin Gnome Wessex HC.2/HU.5; Napier was absorbed by RR in 1961; Belvedere was orphaned. It should have been aborted in 1957.
(prime source: MRH.Uttley,Westland & the British Helicopter Industry,1945-60,Cass,2001.)