I seem to remember BA used to provide a service if you asked and paid for it in advance to be presented on board for special occasions?

Probably wrong of course, and it's just the romantic in me exaggerating. Here's an idea - ask the crew on the QT if you can buy a bottle of Champagne as you want to give it to your wife a surprise for your anniversary? That may make them give you one to take away with you.

If that doesn't work you can always buy her something out of the duty free trolley.........although that could be asking for trouble.