My understanding is that all displays have to be authorised (rubber stamped) before the start of the display season to ensure they are fit for purpose, but more importantly safe for the crew & spectators. However, accidents will still happen.
There was a case in 1983 when an impromtu Lightning display was not authorised, but very sadly the pilot concerned paid the ultimate price when the display went wrong. On this occasion, the pilot concerned was the Lightning display pilot for the season and a very good one (in subjective opinion), however I digress...