In his 1948 The Fine Art of Mixing Drinks, David Embury's says "At some bars a drink served under the name of "Millionaire" which consists of lime juice, slow gin, and Apricot Liqueur, with a few dashes of Jamaica rum. Since the sloe gin, which is a liqueur, predominates in this drink, I do not regard it as a true cocktail." Embury is more complimentary of what he calls a "Millionaire Royal", proclaiming it to be "a very satisfactory drink."
The Sloe Gin Martinez is a brilliant reconstruction of the Classic Martinez. It was created by London Barman, Oskar Kinberg while he ran his own speakeasy style bar Oskar's Bar in the basement of the, now defunct, Michelin Star restaurant Dabbous.