LONDON Shares in WPP fell 4 percent at the open on Monday after Chief Executive and founder Martin Sorrell quit, leaving the group without a boss at a time of huge change in the industry.

Shares in the group, which are already down 30 percent this year, were down 4 percent at 0703 GMT. Analysts and peers have speculated that the group of 200,000 people could be broken up without Sorrell at the helm.

(Reporting by Kate Holton; editing by Sarah Young)