When I was fire officer at Seletar I was in the mess one Sunday morning when I noticed an AAC Beaver landing - the airfield was closed (no fire cover or ATC) at the time. I got hold of SATCO who confirmed he knew nothing about it, but when challenged the AAC Beaver flight, who were resident on the station admitted they just planned the flight without telling anyone, but couldn't see what the fuss was as they landed at unmanned strips in upcountry Malaya all the time.
They had a point I suppose, but it didn't stop them getting a rocket and told to confirm to the regs next time.