Britain’s undersea cables carry the vast majority of its internet traffic. They also represent one of its most exposed vulnerabilities. In early 2026 Russian submarines spent more than a month operating in waters north of the UK, mapping routes that could be severed in any future conflict. The episode, now laid bare by Defence Secretary John Healey, has sharpened focus on both military readiness and the legal framework meant to safeguard this hidden infrastructure. Three Russian vessels took part. An Akula-class attack submarine acted as a diversion. Two specialist craft from Moscow’s Main Directorate for Deep-Sea Research, better known as GUGI, performed the actual survey work. Healey described the operation in stark terms at a Downing Street briefing. “They are designed to survey underwater infrastructure during peacetime, and sabotage it in conflict.” The Akula soon withdrew after being monitored. The GUGI boats lingered. No damage occurred. Yet the message was unmistakable.…