commanded by Lt. Basil C. G. Place, crew S-Lt. R. Aitken, Lt. Whittam, and ERA Whitley; passage crew Lt Philip (commanding), Leading Seaman J. Magennis, Stoker Luck. Vessel was scuttled immediately following the Tirpitz attack, but only Place escaped before she sank. Aitken escaped from the bottom of the fjord, but Whittam and Whitley were unable to escape before their air gave out. Place also earned a VC, Aitken a DSO, while Philip earned an MBE; X8 – unofficially named Expectant, commanded by Lt. McFarlane RAN (Lt. Smart was passage crew commander) X9 – unofficially named Pluto, commanded by Lt. EA Kearon RNVR; AH Harte (Able Seaman) and GH Hollet (Stoker). Foundered on 16 September 1942 while under tow from the Syrtis. X10 – unofficially named Excalibur, commanded by Lt. Hudspeth RANVR The depot ship for X craft was . Builders The numbering sequence of the X class began with X3 because the designations X1 and X2 had already been used previously – X1 had been a one-off submarine cruiser design from the 1920s while X2 had been assigned to a captured Italian submarine. Prototypes X3 – built by Varley Marine, Hamble, scrapped 1945 X4 – built by Portsmouth Dockyard, scrapped 1945 X5-type X5 – built by Vickers Armstrong, Barrow-in-Furness, used in Operation Source, sunk Altenfjord, 22 September 1943 X6 – built by Vickers, used in Operation Source, scuttled Altenfjord, 22 September 1943 X7 – built by Vickers, used in Operation Source, scuttled Altenfjord, 22 September 1943, salved 1976 for museum restoration X8 – built by Vickers, used in Operation Source, scuttled in North Sea, 17 September 1943 X9 – built by Vickers, used in Operation Source, foundered under tow in North Sea, 16 September 1943 with all hands X10 – built by Vickers, used in Operation Source, scuttled in North Sea 3 October 1943 X20-type X20 – built by Broadbent, Huddersfield, used in Operation Postage Able (surveying Normandy beaches prior to invasion) and on Operation Gambit X21 – built by Broadbent X22 – built by Markham & Co., Chesterfield, collided with HMS Syrtis and lost with all hands while training, 7 February 1944 X23 – built by Markham, used on Operation Gambit, sold 1945 X24 – built by Marshall, Gainsborough, used on Operation Guidance (attacking Laksevåg floating dock at Bergen 15 April 1944) when the merchant ship Barenfels alongside the dock was sunk; the dock was attacked and sunk