Fairford a few years back, there with a Puma. Groundcrew decided to doctor the a/c a little. Changed the 3 in the reg to an 8 with a black chinograph, stuck an array of aerials made from paper plates, cups and paint brushes all painted in cam green and stuck on with bluetack. Kept the spotters amused for hours taking pic of the "Sneaky Beaky aircraft" asked lots of questions as to why the reg was not on the register and what were the multitude of aerials to be replied with "sorry cant answer that question its secret".