"U-570"s transmission was in plain language and the British intercepted it. Admiral Percy Noble, commander of Western Approaches Command, immediately ordered several ships to race to the scene. By early afternoon, fuel levels had forced the Hudsons to return to Iceland. The Catalina, a very long-range aircraft, was ordered to watch the submarine until Allied ships arrived. If none came before sunset, the aircraft was to warn "U-570"s crew to take to the water, then sink her. The first vessel to reach "U-570", the anti-submarine trawler HMT "Northern Chief", arrived around 10pm, guided to the scene by flares the Catalina dropped. The Catalina returned to Iceland after having circled "U-570" for 13 hours.