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 forward and to port from 92 station on the centreline of the main flat showing the left bank of cylinders of the port Admiralty Standard Range 16 cylinder diesel engine. In the left foreground is the port main generator abaft the engine.