Brantley, good point. Or therefore a Bell 47H model (Both on the Weston museam site peter).
And the 47H would be noisy... (piston)
Did you get any response from the ATCOs forum. Somebody may remember it as whatever it was would be a bit unusual.
I recall being mistaken for Concorde once by Leeds Approach when flying an R22 towards Menwith Hill. It was the call sign (G-BOYC, which sounds like G-BOAC, a concorde) rather than the speed. Got a good clearence to Coney though, but controller not sure why a concorde would want to land there ...)