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 and slightly to port from 86 station on the centreline of the main flat showing the left bank of cylinders of the port Admiralty Standard Range 16 cylinder diesel engine. Three cylinders are in view and temperature gauges are fitted to all of them. The port main generator is abaft the engine. The escape hatch ladder is down. A vertical format negative.