undetected

It is the architectural equivalent of a stealth airplane, meant to fly undetected—not so much a building as an anti-building.

"They're polite, but they want to catch the traitors, and the traitors want to remain undetected, and both parties are excellent at what they do."

Inside, officers found devices wrapped in foil - an attempt by offenders to transport stolen devices undetected.

Last year, the Electoral Commission was publicly reprimanded for a litany of security failures that allowed hacking groups to spy undetected, after breaking into databases and email systems.

She added: "Xu is a serious danger to women, and without the bravery of victims who came forward, his offending may well have continued undetected."