British holiday company Thomas Cook said Chief Executive Harriet Green had been replaced by its Chief Operating Officer, the abrupt departure of a woman credited with reviving the business sending its shares tumbling. Shares in the world’s oldest travel company fell as much as 23 per cent on news of the abrupt departure plus a warning from the company that growth would slow to ‘a more moderate pace’’ in 2015, to reflect a tougher trading environment. Ms. Green, who joined Thomas Cook in 2012, will be replaced by company insider Peter Fankhauser with immediate effect.