Franz Humer, chairman and chief executive of Roche, is to become chairman of Diageo, the UK spirits group, after the Swiss drugs group said on Thursday it was splitting the two most senior roles at the company.

Mr Humer replaces Lord Blyth as Diageo chairman who will leave on July 1 2008 after eight years as chairman at the owner of Johnnie Walker whiskey and Smirnoff vodka.