A roll film negative. On board the submarine Sealion (1959) towards the end of a long refit at Portsmouth. The photographer is in the control room between 59 and 69 stations on the main flat looking to port and down from 62½ station showing a gauge indicating the keel depth in feet with the diving planes control position and a clinometer below it. On the left is part of the Hydel valve control box manufactured by Vospers. This is the control box for the main tank vent and kingston valves. A vertical format negative.