A roll film negative. On board the submarine Sealion (1959) towards the end of a long refit at Portsmouth. The photographer is in the aft auxiliary machinery and gland space (thrust block compartment) between 103 and 107 stations below the main flat. He is looking up and to port showing a large air bottle against the side of the boat. The port propeller shaft turning gear is on the left and the torsionmeter is on the right. The vertical ladder leading up to the aft accommodation on the main flat is in the right foreground.