Just to clarify my reasoning for my intention to let the plod know, I have had trouble visited on me as a law abiding firearms owner, many times over the past 55 years of going about with anything from an air pistol or rifle in my early teens, on through actual firearms, I have suffered the ignominy of being escorted / visited / detained / or otherwise inconvenienced in some way, sometimes caused by the well meaning, but mostly by those with other intent.
So a simple e mail with details and a pic showing the pinfire mechanism should preclude any nonsense.
I believe in covering all the bases in life, but not to the extent of calling them up every time I want to go shoot.