Peacock had been with Jones Lang in London for 30 years, and helped mastermind the merger with LaSalle Partners to create the international giant that is JLL today. He will retain a consultancy role with the firm. But already thoughts are turning to his successor.

In the short term Stuart Scott will combine the chairman and chief executive's roles, supported by a coterie of senior managers including Peter Barge, head of the Asian operation; Robert Orr, CEO of Europe and Peter Roberts, who heads the American business. All three are among the likely candidates to take over the CEO's desk although under the division of roles agreed at the time of the merger, if the chairman is Chicago-based, then the CEO is most likely to be based in the London head office, which would put the highly-regarded Orr in prime position.

Scott said: "We are beginning our search for a new CEO immediately and, while we expect to move quickly, we will take whatever time is required to select the best person to lead our company." The company said it would not be adjusting its earnings forecasts as a result of the unexpected interregnum.