Yannick Bollore, the 33-year-old son of French tycoon Vincent, was on Wednesday named chief executive of Havas, the world's sixth biggest advertising group. The younger Bollore, who already stepped in for his father as chairman in August, replaces David Jones, who said he was joining a tech-startup after 15 years with the Havas group. Vincent Bollore, one of France's richest men, is the biggest shareholder in Havas and last year became chairman of media giant Vivendi, confirming his push into media. Bollore senior owns a wide array of businesses from operating some of Africa's busiest ports to the recently created Paris electric car rental scheme. Known for his combative nature, Bollore took control of Havas about a decade ago after an epic corporate battle.