The English Channel was Britain's vital sea frontier, but its roughly 29,000 square miles made casual policing impossible, particularly before radar. A useful small craft had to cross to the enemy coast, remain on station long enough to fight, and return before daylight even during short summer nights. That requirement combined speed with endurance and seaworthiness rather than rewarding calm-water performance alone. The geography explains why Channel and North Sea boats evolved differently from craft optimized for other theatres.
Chapter · 17:37-19:10
Channel geography sets the small-craft problem
A Channel patrol boat needed enough speed and endurance to cross, operate near the far shore, and return under darkness across a large search area.