£3.1bn carrier HMS Queen Elizabeth is commissioned in Portsmouth
It is the largest warship ever built for the Royal Navy
Oxford student spared jail seeks appeal
The Queen also took a moment to look at a giant cake modelled on Britain's newest and largest warship.
An Edinburgh cake designer created the 8ft-long (2.4m) edible replica of HMS Queen Elizabeth for the event in Portsmouth.
It took more than 100 hours to complete, and required 7kg of flour as well as 160 eggs.
Wonder how long it will take the thousands of guest to eat though!
The Queen is currently inspecting the front rank of the Royal Guard, while the Princess Royal inspects the rear rank.
The two ranks are made up of 96 members of the ship's company.
The Queen is expected to arrive at the hangar shortly, where she will be met by Adm Sir Philip Jones (pictured, top), the First Sea Lord and Chief of the Naval Staff.
Image source, Royal Navy
Image source, Royal Navy
Image source, Royal Navy
Image source, MODThe new £3bn ship has not been without its critics during the long process to get to where we are today.
Costs have spiralled due to delays and U-turns, while industry figures have said the decision to build two aircraft carriers has come at a cost to Britain's defence.
Dr Peter Roberts, a former warfare officer in the Royal Navy, told The Independent in August, external: "It’s clear that decision... has weakened the defence posture of the UK as a whole.
"The idea that HMS Queen Elizabeth represents national ambition is false, but it might represent a political ambition for a totemic symbol."
The moment HMS Queen Elizabeth arrives in Portsmouth
The 65,000-tonne HMS Queen Elizabeth entered her home port of Portsmouth for the first time back in August.
Thousands of people lined the shoreline turned out to see the 900ft-long (280m) aircraft carrier arrive.
Preparations for the arrival of the flagship of the fleet and its 700-strong company led to more than 20,000 items, ranging from a human skull to sea mines, dredged up from Portsmouth Harbour.
Here's a shot of Katherine Jenkins at the rehearsals for the HMS Queen Elizabeth commissioning ceremony.
She sang a stirring rendition of I Vow To Thee My Country to the assembled crowd.
Image source, Royal NavyYou can watch today's ceremony live on our BBC South News Facebook page, external.
Jonathan Beale
BBC defence correspondent
Image source, ReutersThis is a big day for the Royal Navy. A chance to look to the future and, at least for a moment, forget about recent defence cuts and fears of even more.
After successfully completing her sea trials HMS Queen Elizabeth will be commissioned into service. For the first time she'll raise the White Ensign - officially becoming a Royal Navy Warship.
But, this is still another milestone not the end of her journey. Flight trials will begin next year and her first proper deployment with jets on board isn't planned until 2021. It's also still not clear how many of the new F35 jets she'll carry.
Certainly fewer than the 36 she was built for, with each jet costing around £100m. The Royal Navy believes the carrier - the first of two - will be a potent symbol of British military power. But it's already struggling with limited resources.
Here's a closer look at that cake, an 8ft-long (2.44m) magnificent creation depicting the Queen at the commissioning ceremony.
It will be presented to her at the ceremony to mark the ship's official entry into military service.
Warrant Officer 1st Class William Shepherd, of the Royal Navy, said: "What they have managed to create is outstanding, a real work of art."
You could call it a ship-shape ship cake...
Image source, PA
Image source, PAThe Royal Navy is now live streaming the ceremony on its official Facebook page, external.
Soon to take to the stage, singer Katherine Jenkins...
The £3.1bn carrier and its sister ship HMS Prince of Wales are the most expensive in the Royal Navy's history.
Its hangar could fit two Type 23 Frigates side by side, and its height from keel to top of the mast is the same as that of Big Ben.
But we have even more numbers for you, number fans...
Image source, PAPlates in the hangar of the HMS Queen Elizabeth display the names of some of the people involved in its construction.
Unsurprisingly, it's a very long list!
Image source, Hangar listA ship is nothing without her company, and here are just some of the faces spotted during preparations on HMS Queen Elizabeth ahead of the commissioning ceremony.
They include Lt CdrNick Leeson (top) and Petty Officer Dean Allen (second).
Image source, PA
Image source, PA
Image source, PA
Image source, PA
Image source, PA
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Sam Clayton
BBC Radio Berkshire newsreader
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Firefighters are hoping to track down the owners of a cat which got stuck up a huge tree in Spencers Wood, Shinfield, Berkshire, with a crisp packet on its head.
Workers on a building site in Croft Road spotted the cat clinging to a thin branch yesterday afternoon.
A crew from Whitley Wood used the aerial ladder to get the moggy down.
A Royal Navy steward from Devon is being given the honour of cutting the cake to accept HMS Queen Elizabeth officially into the senior service.
Callum Hui from Lynton has been chosen because - at 17 years old - he's the ship's youngest crew member.
Image source, PA"This is my first ship, straight out of training, and just to have the honour of cutting the cake on commissioning day - it is exciting stuff."
He said the service tradition will be a definite peak in his short career, describing it as "probably one of the stories you tell your kids".
The young steward will be joined in slicing the aircraft carrier cake with a sword by the wife of the ship's commanding officer.
Guests at the commissioning ceremony will include Her Majesty Queen Elizabeth, First Sea Lord, Admiral Sir Philip Jones, as well Steward Hui's mother and brother.