Official HMSO publication paperback original, 64pp, many half tone photo ills, stapled photo pictorial wrappers, 9 x 7", an official account of the Fleet and The Royal Naval Patrol Service ((RNPS) was a branch of the Royal Navy active during both the First and Second World Wars. The RNPS operated many small auxiliary vessels such as naval trawlers both anti-submarine and mine sweeping operations to protect coastal Britain and convoys) minesweepers including a brief history of mine sweeping, training at HMS Lochinvar, how mine sweeping is carried out (with diagrams), a contemporary account of the work including sweeping the war channel and dealing with new types of mine, the sweepers at Dunkirk, etc, ills. include RNPS (Stella Rigel) and Fleet vessels (unnamed)