Weighed anchor & proceeded down Clyde at about 0900. Visibility not good, occasional showers. It was discovered that the after collision mat [Ed: canvas square to be placed over hole in hull] chain had been out by the Port outboard screw and it was possible that the screw had been damaged. Trials were held during the afternoon and also close range gunnery tests, until visibility decreased & it was decided to return to anchorage. Paravanes were streamed with more success than the last occasion.