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 from 81 station on the centreline of the main flat showing the left bank of eight cylinders of the port Admiralty Standard Range 16 cylinder diesel engine. Temperature gauges are fitted to all eight cylinders. A gauge showing keel depth in feet is under the deckhead. The escape hatch ladder is down. A vertical format negative.