Allen & Overy (A&O), Paul Hastings, and Weil Gotshal & Manges are advising as British advertising giant WPP sells a majority stake in its data arm to U.S. private equity firm Bain Capital in a multibillion-dollar deal.

WPP has agreed to sell a 60% stake in its data analytics branch Kantar to Bain in a deal that values Kantar at about $4 billion.

Kantar is a London-headquartered market research business employing more than 30,000 people across 100 countries.

A&O is advising longstanding client WPP with a team led by M&A partner Annabelle Croker, corporate partner Gillian Holgate, and private equity and M&A partner Stephen Lloyd.

Bain, meanwhile, turned to a Weil Gotshal team comprising banking and finance partner Tom Richards, M&A partner Marco Compagnoni, IP partner Barry Fishley, and tax partner Oliver Walker.

Paul Hastings is acting for a group of 10 banks backing the deal – including Barclays, Credit Suisse, Deutsche Bank and Goldman Sachs – with a team led by corporate partners Luke McDougall, Peter Schwartz, Richard Kitchen and Edward Homes; M&A partner Garrett Hayes; tax partner Arun Birla; finance partners Shekhar Kumar and Randal Palach; as well as tax partner David Makso in New York.

A&O advised WPP last year after former CEO Sir Martin Sorrell faced allegations of misconduct, while Weil Gotshal acted alongside Slaughter and May as Bain made a £1.2 billion bid for insurance company Esure.