Britain's Queen Elizabeth this afternoon officially named the Queen Mary 2, the world's biggest and most expensive cruise ship, in a lavish ceremony.

Tight security was in place in Southampton in England for the ceremony at Cunard's 150,000-tonne, £550 million liner in front of 2,000 specially invited guests.

The QM2 will sail on its maiden fare-paying passenger voyage to the US next week.

The launch of the 232ft-high liner has been overshadowed by a tragedy in the St Nazaire shipyard in western France where the ship was built by Alstom Chantiers de l'Atlantique.

Two months ago, a walkway being used by shipyard families on a tour of the liner collapsed and 15 people were killed.