Bypassing WiFi password complexity requirements on a Zyxel wireless router

Last weekend, my broadband provider, Hyperoptic, offered to send me a new wireless router. They promised it’d be a plug-and-play swap. But, since I’m the sort of trouble-maker who does crazy stuff like actually changing my WiFi network name from the stock “Hyperoptic Fibre 4321”, I knew there’d be a wrinkle. Sure enough, when the router arrived and I started modifying its wireless settings to…