From the AAIB accident Report:
"......during the Kingcobra's display, a committee member became concerned by the loss of control at the apex of the first rolling climbing manoeuvre. The committee member attempted to contact ATC five times by radio and the Display Director twice by telephone but he was unable to get an answer."
I witnessed this accident and am appalled that even with 2 methods of communication available the observing committee member was unable to contact ATC and halt the display. I do hope that now a fixed line has been established between the two positions future accidents may be prevented.