A roll film negative. On board the submarine Sealion (1959) towards the end of a long refit at Portsmouth. The photographer is in the auxiliary machinery space between 62 and 68 stations below the main flat looking forward, to starboard and down from 67 station to port of the centreline showing the lower part of the radar periscope well. A klaxon horn is at the top of the picture with an automatic emergency lantern and a 30 lbf/in² pressure gauge below it. An unit marked Aft periscope well heater DB C4C F3 is just above the deck with a wandering lead hand lamp stowed above it. A vertical format negative.