Tantalite
I was also present at that display, ironically the first song I heard afterwards was Volare!
I was with my parents and a school friend who later went on to be a Victor Tanker driver and get a DFC for Black Buck.
The crash was horrendous, I was only 8 and remember it vividly, I was not aware of the speeds involved until reading this site, was also not aware this was a prototype. I knew it had Rolls Royce tech on and that it hit a red & white at the runway end. I think the death toll was 13?
I later served on Vulcans for 5 years in the RAF.
My sympathies to the relatives of the deceased.