Slaughter and May is advising London-based Diageo Plc., maker of Johnnie Walker scotch and Tanqueray gin, on its proposed $2.1 billion purchase of a majority stake in India’s largest liquor company, United Spirits Ltd.

United Spirits is owned by UB Group, the Indian company led by tycoon Vijay Mallya and which also includes United Breweries and Kingfisher Airlines.