Purple Airspace
Parabellum. Purple airspace is a temporary restriction (IIRC 15 minutes before and 30 minutes after published timings- unless it has changed) - are you saying that on the day and in the area in question there was a Royal Flight in the vicinity - in which case perhaps both parties were in the wrong. Or are you suggesting that Purple Airspace is a permanent fixture - which I do not believe to be the case.