 In July 1917, Worsley was appointed commander of the PC.61, one of the later P-boats, with Joseph Stenhouse as his first officer. The PC.61, commissioned on 31 July 1917, was equipped with a semi-automatic 4-inch (100 mm) gun that was hidden by a tarpaulin suspended from crane derricks when not in use. She also had a ram at her bow. Shortly after its commissioning he took his new command to sea on patrol. Most patrols were uneventful but sometimes U-boats were sighted and pursued but these invariably got away. Occasionally torpedoes were fired at his ship. Worsley felt the PC.61 was too easily identified as a Royal Navy vessel against which U-boats were too cautious to make a surface attack. Instead, the submarine would use its torpedoes to attack the ship.
