A nuclear-powered submarine which ran aground two months ago broke down on its first day back at sea, it has emerged.
HMS Astute had to head back to its base in Faslane, Scotland, last week after what officials described as a "minor defect".
Experts identified a fault in the steam plant, which affected the propulsion and desalination system that makes sea water drinkable, the Mail on Sunday said.
It is hoped the vessel will be back in service this week.
HMS Astute became stuck off the coast of Skye in October and ended up marooned for several hours - an error that eventually cost its captain, Cmdr Andy Coles, his command.
Cmdr Coles was replaced by Cmdr Iain Breckenridge.
An MoD statement said: "HMS Astute has been completing sea trials and has returned to port to have a minor defect corrected."