A roll film negative. On board the submarine Sealion (1959) towards the end of a long refit at Portsmouth. The photographer is in the generator room between 77 and 92 stations looking aft at high level from the starboard side of the main flat at 81 station showing the upper part of the 16 cylinder Admiralty Standard Range diesel engine on the right. All of the cylinders are fitted with temperature gauges. Various cable and pipe runs are against the boat's side. A vertical format negative.