Ad giant WPP's shares drop 5% after CEO and founder Sir Martin Sorrell quits
- WPP CEO Sir Martin Sorrell announced his resignation in a letter to staff on Saturday.
- Sorrell spent 33 years at the helm of the business but is leaving after an internal investigation into allegations of misconduct and misuse of assets.
- WPP shares fell 5% at the open in London but recovered slightly.
- Analyst says Sorrell's exit could lead to a breakup of WPP.