five in the afternoon
The first resulted in the release of a small quantity of buoyant wreckage , amongst which was the flagstaff of U75 . The second brought to the surface a quantity of oil , showing that a submarine had been sunk there , but the injuries she previously received had not been sufficient to liberate the contents of the heavy oil-tanks . The explosive charge had completed the destruction of U77 . Just before five in the afternoon , the _ Yealm _ and her consorts passed the eastern arm of the breakwater in Plymouth Sound and brought up in the Hamoaze . Ross and Vernon , arrayed in borrowed clothes and accompanied by Lieutenant-Commander Devereux , lost no time in going ashore and proceeding to the offices of the Commander-in-Chief . `` You are acting with remarkable discretion , '' observed the Admiral , when Ross reiterated his desire not to communicate with his home until the spies were safely under lock and key . `` Fortunately there ought to be no undue delay , as we have two expert Scotland Yard men investigating a case in the Dockyard .