Built by William Gray in West Hartlepool in 1933 the freighter Hartismere had two known encounters with enemy submarines during her career. The first occurred on Aug. 29, 1940 while in convoy OA-204. Oberleutnant zur See Joachim Schepke and his U-100 attacked the convoy northwest of Ireland, his attack was impressive and he sank four ships, but only damaged Hartismere. She was towed to the Clyde and repaired.

On July 8, 1942 Hartismere was en route to Alexandria, Egypt from Lourenco Marques, Portuguese East Africa (modern day Maputo, Mozambique) when in the Mozambique Channel her second encounter with an enemy submarine occurred. On that day the Japanese submarine I-10 and Commander Yasuchika Kayahara, during a very successful cruise, located the unescorted ship. Kayahara during the course of his career sank nine ships, eight of them during this cruise in the Mozambique Channel, Hartismere was his seventh victim.

The ship was torpedoed without warning, fires and an onboard explosion brought the ship to a dead stop and she was abandoned. Kayahara surfaced and shelled the ship until she sank. The forty-seven men on board got off the ship and all made land in Portuguese East Africa. Kayahara made no attempt to dispose of the crew as he had done with the crew of the Donerail just two days after the start of the Pacific war.

Neither I-10 or Kayahara survived the war, it is generally accepted that I-10 was sunk July 4, 1944 east of Saipan by U.S. warships with all hands. Kayhara appears to have been killed in April of 1944, but I have not been able to confirm the cause of his death.