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It's bad luck if the bubbly doesn't break when christening a ship, so P&O recruited the Royal Marines to launch supersize liner Ventura. What are other tricks of the trade?
It is traditional when launching a ship for VIP to swing a champagne bottle at the bows.
But Dame Helen Mirren - the "godmother" of P&O's newest liner Ventura - instead commanded a team of Royal Marines to abseil down the ship and smash the bottle against the hull in Wednesday's naming ceremony in Southampton.
This is because maritime lore holds that if the bottle fails to smash, the ship will be destined for an unlucky life at sea.
Score the bottle
Choose cava - bigger bubbles
Give bottle a good shake
Pick biggest possible bottle - jeroboam better than magnum
Use stiff rope or wire
X-ray boat to find hardest part of bow - and aim there
Last year the Duchess of Cornwall failed to smash a bottle on the side of cruise liner Queen Victoria; later scores of passengers were taken ill with a contagious stomach bug.
To avoid this ill omen, the shipping industry has many tricks to ensure the bubbly breaks.
Champagne bottles are extremely tough, having been designed to withstand high pressure, but it only takes a tiny defect, such as a bubble in the glass, to compromise its strength, says Dr Mark Miodownik, a material scientist at King's College London.
"Glass is a very hard material. If you want to make a defect in it, you'll find it very difficult, but a diamond is stronger. My top tip would be to score the bottle with a diamond."
It's a trick familiar to P&O chairman Sir John Parker, who has launched several ships in his time. "When I was a shipbuilder, we always scored the bottle. Used a glass cutter. It enormously increased the chances of it smashing."
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While the Marines have been practising with scored bottles, Captain Roderic Yapp RM says these smashed so easily against Ventura's hull that an intact bottle will be used in the ceremony.
Dr Miodownik says that mathematical probability, rope type and bubble size all come into it. The bigger the bottle, the higher the mathematical probability of a natural defect, so he recommends using a jeroboam.
Oscar winner Dame Helen Mirren commanded the launch
Forget about vintage, it's bubble size that counts. "The bigger the bubbles, the higher the pressure inside the bottle, the more likely it is to break on impact. The best option is probably to go for a cheap bottle of cava with big bubbles."
And increase this effect by giving the bottle a good shake.
A rope which has any elasticity in it will absorb the energy, so steer clear, says Dr Miodownik. Better than rope would be a length of wire.
While most ship bows are made of rigid steel, some parts will be even more solid than others - so x-ray the bow, locate the groins (main support structures) and take aim for these.
Ship is always female
Woman appointed godmother to act as guardian angel
Never change name of boat - very bad luck
Then there is who - or what - will do the throwing. Ahead of Ventura's launch, a Royal Marine who specialises in ropework and mountaineering conducted a recce of the ship.
Later this month, Royal Caribbean International will do away with the human element altogether when they launch their own large cruise liner.
Their godmother will press a button to activate a special machine to smash the champagne.
But this is by no means foolproof. When Jodie and Jemma Kidd helped launch Ocean Village Two a year ago, the automated mechanism failed to smash the bottle. A crew member on board had to step in and do the honours.