The Queen's granddaughter Zara Phillips performed her first official royal duty at an event unique in British shipping history.
The double ship-naming is Zara's first official royal duty
Zara, 22, and her mother the Princess Royal were in Southampton on Wednesday evening for the first UK double ship-naming ceremony.
In front of 2,000 guests, the princess named the P&O Cruises liner Oceana and her daughter named its sister ship Adonia.
Before the ceremony at the ships' home port, mother and daughter were attended gala dinners on board the respective 77,000-ton vessels.
The princess, speaking before the naming ceremony, provoked laughter by
saying she was slightly surprised at being invited.
Princess Anne toured the bridge of the Oceana
That was a reference to her launch of the P&O ship Aurora in 2000.
On that occasion, the champagne had not broken the first time at the launch - a sign
of bad luck.
The Aurora, also launched at Southampton, then broke down on its maiden voyage and had to limp home.
Princess Anne said: "Thank you for your faith in asking not just one, but two members
of the family tonight."
But at the crucial moment on Wednesday night the Princess failed to break the curse - and the bottle.
When Zara pushed the button to send the champagne crashing against the P&O
Cruises ship Adonia, the bottle broke successfully.
But then Anne's bottle failed to break after she sent it towards Adonia's sister ship, Oceana.
The two ships will spend this summer operating European cruise holidays to the Mediterranean, the Baltic and the Norwegian Fjords.
David Dingle, managing director of P&O Cruises UK, said: "We are extremely excited about the arrival of Adonia and Oceana and feel they will play an important part in realising our vision for the future of British cruise holidays."
Both ships can carry more than 2,000 passengers and 875 crew.
They were built at a cost of £210m each at the Fincantieri shipyard in Italy.