AMBUSH Challenges WESTMINSTER – The new Fleet Submarine AMBUSH has exercised with the Type 23 Frigate WESTMINSTER in the latest stage of the submarine’s trials, including speed runs on and below the surface.      The AMBUSH is the second of the ASTUTE Class submarines, having left builders BAE Barrow last autumn (2012), at the beginning of the long road to operational service.   The WESTMINSTER is the ‘capital ship’ and the lead anti-submarine warfare frigate, under the command of the Captain Anti-Submarine Warfare.