Linklaters and Slaughter and May are among a raft of international law firms advising on a $5bn (£3.2bn) deal to create one of the world's largest advertising agencies.

Tokyo-based Dentsu has agreed to acquire London's Aegis Group, with its largest shareholder – French billionaire Vincent Bollore – selling a 15% stake to Dentsu in a show of support for the deal.

Dentsu is Japan's top ad firm, but has typically relied on partnerships with overseas agencies to reach the international market. Linklaters London partner David Holdsworth is leading the firm's team advising the company on the acquisition.

Hideo Norikoshi, a corporate partner in Baker & McKenzie's Tokyo arm, is advising Dentsu on the Japanese law aspects of the deal, while White & Case London partner Gavin Weir is advising Morgan Stanley as financial adviser to Dentsu on the transaction.

Meanwhile, Slaughters is acting as lead outside legal adviser to Aegis on the sale, with M&A partner Roland Turnill (pictured) and competition partner Michael Rowe in the lead roles.

The magic circle firm previously advised Aegis on its $367m (£289m) acquisition of Australian media buying company Mitchell Communication Group in 2010.

Sullivan & Cromwell is representing Bollore in the transaction, with a team led by Paris partner Dominique Bompoint and London partner Tim Emmerson.

By acquiring Aegis, Dentsu is taking on a company with 12,000 employees in 80 countries that will improve its media buying and digital marketing capabilities.

Aegis' board of directors has already approved the deal, but shareholders have yet to vote on it.

This article first appeared in The Asian Lawyer, an affiliate title of Legal Week.