A roll film negative. On board the submarine Sealion (1959) towards the end of a long refit at Portsmouth. The photographer is in the forward accommodation passage between 42 and 49 stations on the port side of the main flat looking aft and up at the aft bulkhead from 48 station showing various valves, gauges and a klaxon horn above the watertight door and under the deckhead. The fresh water vent and blow panel is on the right.