I-BILL was at Greenham in June 1977 - I remember it well as although I didn't go to Greenham that year, I saw my first P-51 the same weekend - an American one over for a jolly.
I-BILL crashed a month or so later; I believe the canopy departed the airframe during a display at Mainz (?) taking OH-B out of the picture. A very sad loss. And along with Spencer Flack he was very much one opf the founding fathers of the UK warbird movement.
That US P-51D I saw also was ill-fated... back to the US, fatal accident, rebuilt, back to Europe, another fatal accident (might have been the one that robbed us of ace aeros pilot Chris Schweitzer...).
I think if you check back through Flypast Letters pages over the last couple of years, you will find a shot of OH-B flying his Sea Fury (G-AGHB) down the ramp at Duxford at, oh, a few feet or so.