HMAS Tobruk was taking part in a night encounter exercise while participating in SEATO Exercise ASTRA. The opposing forces were designated ‘blue’ and ‘orange’ respectively and the purpose of the exercise was to detect and engage the opposition in a night action environment. Shortly after 21:00 hours Tobruk was steaming as the third, and rear ship, in a Blue Force column lead by HMS Newcastle steering 340 at 25 knots. HMAS Anzac was the second ship in the column ahead of Tobruk. Each ship was 2000 yards apart. At approximately 21:10, star shell bursts were observed by Tobruk to the west of Anzac as the column was executing a turn together to port, to course 160. Several minutes later Tobruk and Anzac were ordered by Newcastle to form on a line of bearing and the course was altered to 130. At 21:17 reports were issued from Tobruk indicating that shells were falling very close to each side of the ship and shortly afterwards she was hit by a shell that passed inboard through the upper deck into ‘A’ gun bay where it detonated critically injuring two ratings: Able Seaman RW Spooner and Able Seaman JR Stevenson. Able Seaman Spooner subsequently died of his wounds. A board of inquiry into the tragedy revealed that a star shell fired from HMS Cockade during the night encounter exercise was responsible for the damage to Tobruk and her casualties.