It may not seem likely now, but at one time England was at serious loggerheads with the Russian Empire.  In response to the threat of invasion in the 1880's, several gun emplacements were established on the coasts of British Commonwealth countries. Sarah Keen visits two of the gun emplacements and writes about them in the Otago Times. The guns stood their ground through both world wars, but only one was fired in anger, allegedly at a friendly ship during WW1 that didn't identify itself quick enough.

Pic of New Zealand gun