However IMO poor airmanship to fly through a notamed display in the manner discribed - the CAA could try a prosecution invoking "reckless endangerment of an aeroplane" if there had been an incident.
I prefer discussing things on this platform rather than have somebody launch an official prosecution, because that only produces pressure and fear, something we have been proud to avoid for a long time and replaced it by "speak openly on pilot errors".
Such prosecutions are double-edged swords and can be quite complicated.
Just as a speculation, if there would be an incident, the "reckless endangerment of an aeroplane" may as well fall onto the display training pilot and his organization. The balance of responsibility between display pilot and intruder may be fragile to judge.
If the intruding pilot was legal on entering and did document his thorough preflight preparation and was legal in not calling on the radio and there is an incident in the situation we speculate on, it may be a simple pilot misinterpretation of the danger of the, to him unknown, aircraft on display training and maybe not so well airmen-ship, something which is independent of the law. But, the other than usual awareness asked from that pilot is also only for a short period.
On the other hand, the pilot of the display training aircraft does steer a to him well known aircraft with the respective danger awareness and he has to be fully aware of it to be eligible for such a mission. Even further, the display pilot has to be always right on spot in awareness about the training, its danger, the area covered and the possibility of other aircraft entering, if the NOTAM was issued that way. If there was potential foreseeable danger for an ordinary skilled other pilot legally entering the NOTAM'ed airspace, the safety management of the display organization will be on investigation.
I am unable to predict the outcome of such prosecution.