TBML: WG.13 (to be Lynx) is the only production helicopter wholly designed in Yeovil. WG.34 began mid-1978 solo, but by 11/79 it had become joint with Agusta, to be EH101 Merlin. Yeovil built (ex-Hughes) AH-64, and Sikorsky S.51/55/58/62. Agusta began on Bells, then Sikorsky S.62; its Meridionali Unit did Boeing-Vertol CH-47.
Eurocopter's French half (once Sud) began on S.55/58, then was World-first with successful turbine types, Djinn and Alouette. Its big ASW Frelon had a Sikorsky power-train sub-licenced from Agusta. The German half (once MBB) entered the sector with original Bo.105 and licenced its rigid rotor to Sud who schemed Gazelle with it, then dropped it.
It would be complex to trace paternity of rotory power-trains. Juan de la Cierva UK-patented cyclic pitch control, dying before he could hover; by ’42 a Russian-American did. MRH.Uttley,Westland & the Br.Helicopter Industry, 45-60,Cass,2001,P110 recounts that in 1944 UK requested 250 Sikorsky R-5A (HO2S-1), asserted patent infringement, was berated by Senators (US supplies were free!), and let the order, and the issue, lapse.