ARU

From Airsoft Community Wiki

An ARU or Armed response unit is an arm of the police service, a few airsofters around the country have been subjected to "theres a man with a gun in the next door neighbours garden" calls to the police and have been investigated by an ARU.

If your garden is visible to your neighbours please take the time to explain to them that they are only "BB guns" and that you are not a raving lunatic to avoid unpleasent meetings such as this.