Britain’s largest ever warship has squeezed out of its dockyard, as the ship heads out on sea trials. The 65,000 ton HMS Queen Elizabeth slipped out of Rosyth dockyard and into open water through an exit with only 14in clearance on either side and 20in of water under the keel.The aircraft carrier then edged along the Forth under three bridges, including the landmark rail bridge, with a little over six feet to spare. After trials begin this summer, the ship will move to its new home in Portsmouth this autumn. Trials for planes and helicopters will take place next summer.The flight deck is more than four acres in size and the ship can carry up to 36 F-35B stealth jump jets. The arrival of the new carrier comes as the Navy is facing a budget black hole of around £500m each year and the demands of manning the new ships have been accused of causing shortages elsewhere.Critics of the carriers have also claimed they are expensive white elephants that are too vulnerable to new high speed missiles. He said: “We will go where it’s best to go and not where it’s best for a Soviet nuclear to go, so the reality is we can probably look after ourselves as long as our escort is in the right place at the right time. You don’t have to hang around and endure it, you can move away and go somewhere else.” HMS Queen Elizabeth on the Firth of ForthCredit: Andrew Milligan/PA The aircraft carrier squeezes out of dock to begin sea trialsCredit:Jeff J Mitchell/Getty Europe Bosuns mate Scott Campbell guards the Navy’s new warshipCredit:Getty The trials mark the latest milestone in the nearly decade-long building of the Royal Navy’s two carriers, at a cost of more than £6bn.The Navy is also preparing for the warship’s first appearance to attract a concerted Russian spying effort, with submarines, ships and planes try to get a good look at the UK’s new flagship. The first steel was cut on the carrier eight years ago but it will not be sent on operations until 2021. Early deployments are expected to see US Marines F-35B jets embarked alongside British planes, to make up for early shortages of UK jets.The Royal Navy has not had an aircraft carrier since the defence cuts of 2010. Capt Jerry Kyd, commanding officer, said: “There is nothing on the globe that is invulnerable, whether that’s a city, a car, an individual, or a ship. We are not shy in the military to understanding the risks and how we mitigate that in the theatre of war. The radio mast has been lowered to allow the vessel to pass under a bridgeCredit:Andrew Milligan/PA “If you look at all the premier nations around the world, why is it that every nation in the top tier is investing billions of dollars in aircraft carriers? Is it just us, or has everyone got it wrong? The reason being is that they provide the government, very simply, with an incredibly flexible tool. It’s not just about war-fighting. This is about deterrence, coercion, signalling, proving a huge sea base for disaster relief, humanitarian assistance, defence engagement.” Want the best of The Telegraph direct to your email and WhatsApp? Sign up to our free twice-daily Front Page newsletter and new audio briefings. He said 2021 “will be the first time we will deploy this ship in anger”. A Royal Navy warship is expected to escort HMS Queen Elizabeth, while shore-based helicopters look out for submarines as commanders try out the warship in the North Sea and Moray Firth.Cdr Fiona Percival, head of logistics on the ship said: “[The Russians] will come and look, but they look at everything.”Cdr Mark Deller, commander air, said the ship would be accompanied by a frigate or destroyer. Commanding Officer Captain Jerry Kyd onboard the HMS Queen Elizabeth Aircraft Carrier at Rosyth DockyardCredit:Getty The warship under steam off the coast of ScotlandCredit:Andrew Milligan/PA The carrier’s flight deck is more than four acres in size HMS Queen Elizabeth is pulled by tugs under the Forth Rail Bridge in the Firth of ForthCredit:PA A simulation of the 65,000 ton vessel being squeezed out of the basin at RosythCredit:BAE Systems plc Ian Booth, managing director of the defence industry alliance behind the ships, said: “The incident with the fire in London really brings it home to you, you don’t take chances with any incident on the ship, whether it be flooding or fire.” Sailors and engineers have worked round the clock getting the vessel ready. A total of 1,000 sailors and contractors will be onboard for the first six weeks of testing. Crew have spent hours each day carrying out safety drills for fires, flooding and personnel overboard. More than 650 doors and hatches have been checked to ensure they are watertight and fire safe.