Kraft Foods' pursuit of Cadbury took an unexpected twist today after lead advisor and legendary dealmaker Bruce Wasserstein was taken to hospital with an irregular heartbeat.

Investment bank Lazard, where Wasserstein is chairman and chief executive, said the 61-year-old New Yorker was in a serious but stable condition.

His sudden admission to hospital triggered uncertainty over Kraft's £10 billion-plus bid for Cadbury.

Kraft and Cadbury have been trading punches since the US firm made public its proposed bid for the British chocolate giant on 7 September.

Cadbury turned down the 745p a share bid on the same day, arguing that it seriously undervalued the company.

Kraft is now expected to wait until after Cadbury's third-quarter sales update, due on 21 October, before making its next move. It has until 9 November to “put up or shut up”.

Observers said Wasserstein's health problems were a blow to Kraft — he has been very hands-on in his approach to the deal — but added there are many other bankers advising the firm.

Campbell Harvey, a professor at Duke University's business school, said: “This is a person that's deeply involved in the relationships that are so fundamental to his company. It just screams of uncertainty.”

Wasserstein achieved fame as an advisor to KKR on its acquisition of RJR Nabisco in 1989 which was recorded for posterity in the book Barbarians at the Gate.