The British Aircraft carrier HMS Queen Elizabeth is berthed in its Dock before its maiden voyage, in Rosyth, Scotland, Britain June 21, 2017. [Photo/VCG]

LONDON - The largest and most powerful ship ever built for the British Royal Navy left port Monday to start sea trials ahead of going into active service, the Ministry of Defense announced in London.

HMS Queen Elizabeth, a 280-meter, 65,000-tonne aircraft carrier set out from Rosyth on the Firth of Forth in Scotland, carrying a crew of 700 to undertake maiden sea trials over the summer.

The carrier, built at a cost of almost $3.9 billion will become the Royal Navy's flagship and will be joined later by a sister carrier, HMS Prince of Wales.

The warship successfully left her port after a delicate manoeuvre, which saw navigators, river pilots and tug boats working with the slimmest of margins of just a few centimeters, to guide HMS Queen Elizabeth out of the Rosyth basin where she was assembled.

At high tide the ship was taken through a narrow gate avoiding the dock walls by inches, while under the water line there was just half a metre between the bottom of the ship and the sea bed.

Commanding officer Captain Jerry Kyd said: "We had to be very careful, but you practise it and drill it and rehearse it to make sure we do it safely in a timely fashion because the tide waits for no man."

Once in the Forth, the carrier must then wait for the tide to lower to pass under the Firth's famous bridges.

Around 10,000 people worked on the construction of the carrier, which was made up in sections at shipyards around Britain, and then transported to Rosyth where it was assembled.

The second ship in the class, HMS Prince of Wales, is already being fitted out in the same dock.

The sea trials will take place in the North Sea before the carrier returns to Rosyth for further checks and any adjustments.

Captain Kyd said: "At the end of that period we know that all the basics work. She's done her test drive and after that we will go down to Portsmouth, the ship's home, and get her finally ready to join the Royal Navy fleet, hopefully at the end of the year."

Defense Secretary Sir Michael Fallon said: "This is a historic moment for Britain as our new aircraft carrier takes to sea for the very first time. This floating fortress is by far the most powerful ship ever built in Britain that will enable us to tackle multiple and changing threats across the globe.

"HMS Queen Elizabeth is an enduring example of British imagination, ingenuity, invention that will help keep us safe for decades to come. She is built by the best, crewed by the best and will deliver for Britain.

"For the next fifty years she will deploy around the world, demonstrating British power and our commitment to confronting the emerging challenges from a dangerous world. The whole country can be proud of this national achievement."

Admiral Sir Philip Jones First Sea Lord and Chief of Naval Staff said: "This is a hugely significant moment for the Royal Navy, for all our Armed Forces and for our island nation. Once in service HMS Queen Elizabeth will be the largest aircraft carrier in the world outside the United States, and the first designed from the outset to operate a fifth generation aircraft."