Andy says...

The perfect cocktail for Christmas morning

Created in 1921 by Malachy McGarry at the Buck's Club,18 Clifford Street, Mayfair, London (Est. 1919).

McGarry himself was a featured character in the works of P.G. Wodehouse, as a bartender at the Buck's Club.

This is the precursor to the Mimosa which was invented 4 years later by Frank Meier at the Ritz Hotel, Paris.