Corporate raider and Havas chairman Vincent Bollore has increased his stake in London-based Aegis Group, parent of the Carat media agency network, to nearly double what it had been a week earlier, reaching 11.38 percent, reports Adweek. The move follows news that Paris-based Publicis Groupe held talks with Aegis about an acquisition.

Accordingn to U.K. takeover laws, the buyer of a public company has to accumulate more than 90 percent of the company's shares, else remaining shareholders can force the company to remain listed on British stock exchanges.