Ivan Menezes celebrated his success landing the job as boss of the world's biggest drinks company, Diageo, with a glass of Johnnie Walker Blue Label whisky on the flight from London to New York. The promotion of the chief operating officer and company insider didn't scare the horses in the City as the shares barely twitched. But as he sipped the £130 liquor on the plane Mr Menezes might well have pondered the shoes he will have to fill when Paul Walsh, the FTSE 100's third longest-serving boss, departs.