Turning bow on to the contact, the tracking crew quickly set up to track the target. After forty five minutes, the crew had worked the base course and speed needed to conduct an approach. Even though the target was making only 7 knots with a moderate zig zag pattern, the sub had to do a two hour end around to reach a firing position. The Captain elected to make a submerged approach since the target had been identified as a Tribal class destroyer. However, during one of the periscope observations it was realized that the ship was not a 2000 ton destroyer, but rather a 9,000 ton Leander class cruiser. Furthermore, the vessel appeared to have a slight port list and was sitting lower in the water than normal.
The error in target identification, easy to make on a moonless night, meant that the wrong mast head height had been used, and that meant that any torpedoes fired using that solution would be misses. The executive officer worked furiously with the tracking crew to work out the correct solution with the new target data. The error in the mast head height meant that the range to target was greater than anticipated. Lowering the periscope, the Captain had to make a high speed run to reach the newly calculated firing position. This nearly exhausted the battery since the sub had just been in the process of starting her nightly charge when the target had been sighted. Luckily, the target's zig zag pattern held to prediction and the submarine was able to loose a full spread of torpedoes at the target from a range of 1500 yards.
One hit was observed, and after which the target's engines and propellors were heard to stop.
Through the periscope the Captain could see the fires burning on the cruiser, highlighting the details and camoflague pattern. At this point he realized that the vessel was the same ship that they had torpedoed and reported sunk two days earlier. While disappointed that this was not a second Leander class cruiser, he was still grateful to know that he had indeed put the Achilles under, even if it took three days to do so.
Again, though, he was unable to stay on the scene until the cruiser sank. The batteries were nearly flat and with their proximity to Sydney, they would have to pull away from the cruiser, surface, and charge their batteries before sunrise. The dawn would surely bring a swarm of hunting aircraft and possibly rescue vessels to the scene.

















