Alistair Darby, Chief Operating Officer of Pedigree bitter brewer Marston's, is off on a pub crawl of sorts, moving to rival pubs group Mitchells and Butlers to become Chief Executive.Peter Dalzell, Managing Director of Marston's Inns and Taverns, and Stephen Oliver, Managing Director of Marston's Beer and Pub Company, will now report directly to Ralph Findlay, Marston's Chief Executive Officer.Since rejoining Marston's in 1997, Darby held a number of senior operational and strategic roles, including leadership of its branded and suburban managed pubs, its beer division and its tenanted and leased pub company. He was appointed Chief Operating Officer in 2011.Darby will take up his role as Chief Executive on 8th October 2012. Following a short period of induction and handover, Bob Ivell will revert to the role of Non-Executive Chairman. JH