Supplying the many needs of H.M. Submarines, depot or "parent" ships performed indispensable service during the war at sea. When a Submarine returned from a lengthy patrol its crew needed rest and relaxation and a brief change from cramped living conditions; their vessel required revictualling, refuelling and rearming, perhaps minor repairs or a general overhaul. These requirements were administered by a depot ship, as and when necessary. Somewhat staid in appearance but costly to construct, these specialised ships were splendidly equipped with workshops for on the spot repairs of Submarines as they came alongside. For the Submarine crews there were comfortable quarters including recreation rooms, bars, a well stocked library and even a cinema. The drawing depicts a Submarine moored alongside and the business of rearming it with torpedoes is in progress. Taken from the depot ship’s store, torpedoes were charged with compressed air (providing the motive power), and the explosive heads were fitted; they were then swung outboard by electric crane (A) and lowered for stowage by members of the submarines crew (B) others are attending to the gun (C). Returning to the depot ship, (D) is the fire director tower, (E) chart house, (F) periscope derrick, (G) searchlight tower, (H) multiple A.A. guns, (J) galley, (K) dual purpose guns, (L) cabins, (M) heavy electric crane, (N) motor boats. These ships of which the above was a typical example, varied from some 5,000 tons displacement to over 12,000 tons, with a speed of 14 to 17 knots. In addition to carrying supplies, and spares for effecting repairs it had on board trained men for the replacement of any Submarine crew members who may have been sick or injured as a result of an action.