I recall watching the rehearsal for this on the airfield at Weston super Mare with John Dowling as the pilot. It all went pretty well,dropping the "spire" into a measured hole in a wooden block atop some scaffolding. The engineer at Westland who did all the calculations etc went on to work for BEA Helicopters at Gatwick as I recall and transferred his skills to S-61N external load contacts. Can't recall his name ??