The submarine was towed to Þorlákshöfn, Iceland, and beached there for essential repairs, then towed to Barrow-in-Furness where she was fully repaired. By the time the Royal Navy had taken possession of U-570 the German submariners had destroyed all their code books and coding equipment. As a consequence of this, there was no need to keep her capture secret (unlike in the case of U-110, which had sunk whilst under tow, but not before its codebooks and Enigma machine had been retrieved).
U-570 was commissioned into the Royal Navy as HMS Graph on 19 September 1941, and assigned the Royal Navy pennant number N46. She was given a name beginning with a 'G' to signify German, i.e., denoting that Graph was a captured vessel. She saw active service in 1942 and 1943.
On 21 October 1942, in the Bay Of Biscay, about north-north-east of Cape Ortegal (,), she encountered the U-333. Four torpedoes were fired but all missed. In December 1942, HMS Graph sighted the German cruiser Admiral Hipper on her return to Altenfjord following the Battle of the Barents Sea, but Hipper was traveling too fast to be attacked. Three hours later Graph sighted one German destroyer towing a second, and attacked. However, her torpedoes missed.
Defects, exacerbated by a shortage of spare parts, led to her being placed in reserve, and she was decommissioned from active service in February 1944. She was being towed by HMS Allegiance to the Clyde for scrapping when she ran aground on the west coast of Islay, Scotland, on 20 March 1944. She was partially salvaged and scrapped in 1947. Some remains of HMS Graph remained visible at low tide on the rocks near Saligo beach on the West coast of Islay at least into the 1970s, with the pressure casing of the conning tower and periscope tube clearly visible (the cladding and railings etc all washed off in the Atlantic storms many years before.)
One of the Kriegsmarine flags of the U-570 was presented to the Hudson bomber pilot, Sqn Ldr Thompson, and is now part of the collection of the RAF Museum.