So much could be said in sadness, but I'll restrict myself to this: I did a bit of an interenet search and ended up at Wikipedia (FWIW*). I could find very few casualties recorded amongst non-participants (by which I include spectators, whether official or unofficial), and none in the UK.
Is it really correct that this is the first time ever in the UK that passers-by, unconnected with the display, have been killed or seriously injured by a display accident?
MB
*
https://en.wikipedia.org/wiki/List_o..._and_incidents
I don't think it is. They are just harder to research the further you go back in time and when death by accident was more commonplace.
For example there is this incident which is hardly recorded other than in this link:
ASN Aircraft accident 18-SEP-1948 de Havilland DH.98 Mosquito FB.Mk VI TA507
( ten killed in a hospital)
The 18th September 1948 was a particularly bad day for Mosquitoes with three of them being involved in fatal crashes during air displays at different locations. The one at Manston also killed ten on the ground but in that incident I think those would be technically classed as spectators as they were on the road leading into the air display.