any picture taken in the course of one's duty is automatically Crown Copyright.
That may well be the case if you are a military photographer, or photography is within your terms of service ie in the days when an AEOp would photograph vessels from the beam window. The rule of thumb remains: Who owns the camera? ..for he who owns the camera owns the image.
If you use your own camera and you do not have a remit to take photographs formally, the copyright is yours regardless of subject matter. This does not provide protection from the Official Secrets Act and could still get you a visit to your AOC. ....and I should know
To encourage photography with 'Photograph of the Year' competitions and then discipline you for taking photographs is clearly a case of mixed signals or conflict of interest. There is not a plane in the sky that has not been photographed by someone with a fortunes worth of long lens; Area 51 may prove me wrong, but you get the drift. However a short camera phone video of impending doom is a little embarassing especially when on youtube: Que "Ye have little faith" said the Apache pilot, seconds before "Mayday..."!