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 below the main flat between 77 and 82 stations, this space being irreverently known as the snake pit. He is looking to starboard and up from the centreline at 78 station showing the ladder leading up to the main flat with the distilling plant control and instrument panel behind it. Above the control panel is the Reavell H.P. air compressor. A vertical format negative.