Herbert Smith Freehills and Slaughter and May are advising on British beverage giant Diageo's £1.2bn purchase of a 53.4% stake in Indian drinks company United Spirits.

Herbert Smith is acting for United Spirits and parent company United Breweries led by City corporate partners Alan Montgomery and Roddy Martin alongside India practice chairman Chris Parsons.

Indian firms Amarchand & Mangaldas & Suresh A Shroff & Co and Kanga & Co are advising on local law aspects. United Spirits owns brands such as Whyte & Mackay, Black Dog and McDowell's No.1.

Slaughters is advising Diageo led by corporate partners Simon Nicholls, Robin Ogle and Padraig Cronin alongside finance partners Stephen Powell and Ed Fife, tax partner Sara Luder, intellectual property partner Susie Middlemiss, employment partner Charles Cameron and real estate partner David Waterfield.

Indian legal advice is being provided by Platinum Partners with corporate partners Nihar Mody and Yash Mohanram.

Herbert Smith's Martin said: "This is a great emerging markets story. The deal will see Diageo break into the Indian market and the combination of their premium brands with United Spirits own strong brands and their knowledge and reach of the Indian market is very exciting."

The transaction has seen an initial purchase of a 27% stake in United Spirits by Diageo for £660m, which will be followed by a number of subsequent share purchases over the coming months in compliance with local law, expected to be concluded in early 2013.

The news comes after Diageo, which owns alcoholic beverage brands including Guinness, Baileys, Captain Morgan and Smirnoff , tapped up US investors in May this year, issuing a total of $2.5bn (£1.6bn) in bonds split into five-year, 10-year and 20-year maturities.