After a £35 million makeover, HMS Northumberland has begun sea trials off the South West coast.
The Type 23 frigate entered service in late 1994 and was built in the North East by the Swan Hunter yard.
However, for the last two years HMS Northumberland has been in Devonport, undergoing an extensive refit which included a repaint, structural work and, most notably, being armed with the new Sea Ceptor missile system.
The Sea Ceptor, which replaced Sea Wolf missiles, can travel up to three times the speed of sound with a range of more than 15.15 miles.
It is hoped that the vessel will be operational by Christmas as part of the Navy's arsenal in anti-submarine warfare.
"The sea trials really are our opportunity for ourselves and our Babcock partners whose conducted the refit, to ensure everything that's been fitted and worked on is functioning correctly and we're ready to go back out into the fleet as an operational, capable unit."
The frigate got off to a rough start on the sea trials after problems with the diesel generators, which was later resolved.
Leading Engineer Technician Daniel White said: "It's quite exciting, I can't wait for the first firing (of the Sea Ceptor missiles), it's not going to be as much of a 'woosh' as the Sea Wolf but it's still going to be a fascinating watch."
Lieutenant George Wheatley said: "The people that are putting on the breathing apparatus, that are rigging hoses and that kind of thing, we want them to feel that it's a real exercise so they get the adrenaline pumping without losing control.
"I think as officers and the people that are in charge of each sections of the ship, it's important for them to remain calm and have an oversight of what's going on."
The vessel has also undergone a crash exercise, replicating an aircraft crash on the flight deck and putting the crew through their paces.
After passing the test, crew onboard HMS Northumberland were given the green-light to begin flight trials.
The Merlin Mk 2 on HMS Northumberland is designed to hunt submarines and has its own submarine tracking kit.
Mohawk Flight Commander, Lieutenant Commander Mike Howe, said: "We are at the ship's disposal, we're one of her many assets that she can put into the fight.
"So we would go with either tasking or search roles and go out and offer what the Mk 2 is designed to do, which is hunt and kill."
HMS Northumberland is currently midway through her sea trials and later this week will visit her affiliate and namesake county for a rededication service in Newcastle.