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 the centreline of the main flat at 81 station showing the upper part of the two 16 cylinder Admiralty Standard Range diesel engines. On the right is a gauge showing keel depth in feet and on the left is a pressure unit, possibly a barometer, labelled 'instrument illumination L.P. fuse panel M6'. All of the cylinders are fitted with temperature gauges. The ladder up to the escape hatch has been rigged. A vertical format negative.