According to decanter dot com, the official Champagne of the royal wedding will be NV Pol Roger.

(Good choice if you can’t acquire a sufficient stock of the 1998, 1996 or 1995, say I.  Prince Charles and the late Princess Diana chose Bollinger; so, perhaps that marque would have been regarded as bad luck.)

As Champagne fans know, Pol Roger had many twentieth century associations with the British government, although generally with commoners rather than royalty, particularly Sir Winston Churchill after whom their prestige cuvee is named.  One of my favorite stories is about Lord Soames, giving a press conference during Rhodesian peace talks way back when, predicting that the talks would be concluded within less than 30 days.  Asked how he could be so confident of an early conclusion, he revealed that his remaining stock was only twenty-something bottles of Pol Roger.

Cheers -