It was almost midnight when a truck driver resting in his cab heard the crackling of flames at a warehouse in east London storing equipment for Ukraine. About 30 minutes after the fire started, Dylan Earl, a British man who admitted to organizing the arson, received a message from a man U.K. authorities say was his Russian handler. On Tuesday, a British court found three men guilty of arson in the March 2024 plot that prosecutors said was masterminded by Russia’s intelligence services — part of a campaign of disruption across Europe that Western officials blame on Moscow and its proxies.