Slaughter and May, Freshfields Bruckhaus Deringer and Linklaters are advising Vodafone and Three UK on on one of the U.K.’s biggest ever mergers of telecoms companies.

Slaughters is advising Vodafone, according to deal documents, while Freshfields and Linklaters are advising CK Hutchison, owners of Three, on antitrust matters, and corporate matters respectively.