UK's new £3.1billion aircraft carrier was welcomed by the Queen at a ceremony to commission it into the Royal Navy fleet.
The carrier stands at 280 metres in length and with an estimated half a century working life, the 65,000-tonne carrier is the most powerful warship that the UK ever built.
In attendance was the Queen, Princess Anne and First Sea Lord Admiral Sir Philip Jones along with 3,700 guests in Portsmouth, Hampshire.
The Queen arrived on board using a specially installed lift and was shown around by the ship's commanding officer Captain Jerry Kyd. Theresa May was also scheduled to attend but she canceled due to the ongoing Brexit talks.
The Queen said of HMS Queen Elizabeth, which has been dubbed Big Lizzie: 'A true flagship for the 21st century.
'The most powerful and capable ship ever to raise the white ensign, she will in the years and decades ahead, represent this country's resolve on the global stage.'
Upon her arrival, the national anthem was played before the Queen and Anne inspected a guard on parade. After which she received the royal salute as the white ensign was raised for the first time on the flight deck, broadcast into the hangar on large screens.
An audible sigh of relief could be heard from the ship's company as the ensign, initially slightly entangled, opened out fully and flew freely in the wind.
The Queen made a statement saying: 'We are gathered here in Portsmouth today, just a short distance from HMS Victory, a flagship of our seafaring past and a reminder of the debt we owe to the Royal Navy, which, for more than 500 years, has protected the people of this country and our interests around the world.
'Like HMS Victory, HMS Queen Elizabeth embodies the best of British technology and innovation.
'At the forefront of these responsibilities will be the men and women of the Royal Navy and Royal Marines, supported by the Army, Royal Air Force and by coalition partners.
'As the daughter, wife and mother of naval officers, I recognise the unique demands our nation asks of you. I will always value my special link with HMS Queen Elizabeth, her ship's company and their families.
'As you prepare to take this country's message of peace, partnership and prosperities across the seas and oceans of the world, the lord high admiral, the Duke of Edinburgh, joins me in wishing you well in all your endeavours.'
There were also cakes created for the event including a scale model of the carrier and others depicting the Queen and sailors on parade, including one fainting sailor shown fallen on his face were on show.
The event was organised to commission the carrier into the fleet but the Aircraft Carrier Alliance confirmed that the Navy had formally accepted the ship on Thursday, meaning it had been fully handed over to the MoD.
Defence Secretary Gavin Williamson also attended to witness the huge vessel being welcomed into the fleet.
He said today: 'It is an honour to witness the crowning moment of an extraordinarily busy year for the Royal Navy that has seen us name the second carrier, HMS Prince of Wales, cut steel on the first Type 26 frigates and launch the National Shipbuilding Strategy.
'Our new aircraft carrier is the epitome of British design and dexterity, at the core of our efforts to build an Armed Forces fit for the future.
'For the next half a century both carriers will advance our interests around the globe, providing the most visible symbol of intent and commitment to protect the UK from intensifying threats, wherever they may come.'
'We have been working, the Navy have been working, the Ministry of Defence have been working to get it ready for the last 20 years. This is a very important moment.' The ceremony concluded with the cake representing the ship being cut by the commanding officer's wife Karen Kyd and the youngest member of the ship's company Steward Callum Hui, 17, from Lynton, Devon. Describing the moment, which is a service tradition, as a definite peak in his short career, he said: 'It will probably be one of the stories you tell your kids'.