Guest Stars Orla Russell as Poppy Lois Chimimba as Tara Kierly Bobby Rainsbury as Cronin Cristian Ortega as Anderton Martin Compston as Chief Petty Officer Craig Burke Reuben Joseph as Porter Tom Gill as Chief Petty Officer Adams Therese Bradley as Laura Michaels Oliver Lansley as Mark Hill Aisha Toussaint as Cat Parth Thakerar as Jay Kohli Dan Li as Hennessy Nebli Basani as Digital Operations Officer Angelique Fernandez as Admiral Scott Jordan McCurrach as Signals Operations Silvie Furneaux as Prentice's Daughter Jack Sherlock as Hull Valve Engineer