May I suggest an alternative version of events:
Spitfire joins for his normal impressive air show arrival 'beat- up ' and at the last moment seeing a nice fat target decides to ' wake it up !
The innocent Chinook ( who did everything right ) takes umbrage and files an airmiss.
However was there any real danger of a collision ? I think NOT - unless the helo ( which was probably thought to be on the ground ) suddenly rotated into the path of the oncoming Spit - and even then the alert Spit pilot with a quick twitch of his sensitive controls would have avoided trouble.
Whilst not condoning what was obviously a very irresponsible action , thinking back in the distant past I can think of many similar events such as Lightings in reheat beating up Vulcans on the ORP , and Vulcans having ' a go ' at innocent Camel Trains and Sanpans !! Or Nimrods waking up unsuspecting container ships etc etc !
The real fright comes when ,usually flying VFR in a low sun,smoke or heat haze an aircraft,glider or balloon flashes by totally unseen until too late!