I, too, was there when the mini-Mustang went in. The barrel roll has long been a big killer of display pilots.
The F 1/11 did its fast pass at Manchester instead of at the Woodford airshow. I did my RT exam in 1978 with the controller who was on 'Manchester Approach' that day. He told me he saw the primary return coming across the Pennines at several miles per 'paint', and soon realised it was headed for Ringway instead of Woodford. It was, of course, on the Woodford frequency so the Manchester controller picked up his phone to advise Woodford of the situation. As he did so, he heard the roar of its low pass past his tower!
It missed an approaching Vanguard east of Stockport, and a Viscount climbing out over Knutsford, did a big 'U' turn, and went back east, home and probably unaware of his mistake (until he landed at base!).
The USAF could often not find Barton - the RAF always did. Some US display aircraft went fuel critical trying to find us, so never got to the show, and one F 1/11 did one fast pass, turned left, and lost the field. He never found it again before he had to go home due fuel critcality!