As Geehovah has said: RIP chaps, it was nothing to do with any rolling manoeuver, they failed to get round the bottom of a loop.
I'd left the F4 when the accident happened but knew Chris well and had met Jack a few times. Any further comment is best left to the official report, here:
http://www.mod.uk/NR/rdonlyres/B51B5...8_23sept88.pdf