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 to port and down showing the port propeller shaft turning gear. The end of a Johnson lathe is in the right foreground with the shaft torsionmeter beyond it. A large air bottle is against the port side of the boat. A vertical format negative.