The Russian Scares were a real thing, even in the far outposts of Empire. As a kid I used to run around these fortifications at the entrance to Auckland, now sadly much safer to visit!
https://www.doc.govt.nz/parks-and-recreation/places-to-go/auckland/places/maungauika-north-head-historic-reserve/north-head-historic-reserve-history/history-of-the-reserve/