Her Majesty was at the centre of the ceremony, accompanied by the Duke of Edinburgh. Today's celebration was likely to have been nostalgic for the Queen, as the P&O new liner bears the same name as the royal yacht Britannia, in service from 1954 to 1997.
Accommodating more than 1,350 crew and 3,600 passengers, Britannia is the largest cruise ship specifically designed for the British cruise market.
The newest addition to the fleet of P&O boasts 15 passenger decks, 13 places to eat and 13 bars, a 3-tier atrium, 936-seat theatre, 4 swimming pools, and multi-million pounds art collection.
The £473 million liner also has a spa and extensive kids’ areas, a gym, sports arena, library and shops.
Britannia’s passengers will take part in an onboard cookery school and there will be guest chefs, including Mary Berry, James Martin and Marco Pierre White.
Captains Paul Brown (with P&O Cruises since 1989), and David Pembridge (with the company since 1972), will rotate being in command of the ship.
Sailing from Southampton during summer months and in the winter operating from the Caribbean, Britannia will call at 57 ports in 31 countries during her first year, traveling over 90,000 miles.