Sir Ian Gibson, the long-running Chairman of Wm Morrison, has revealed his intention to step down next year.Gibson, who joined the supermarket chain as Non-Executive Deputy Chairman in September 2007 and was appointed Chairman in March 2008, will not seek re-election at next year's annual general meeting.In a short statement on Thursday, the company said it will begin to conduct an "orderly process to appoint a successor"."The board welcomes Sir Ian's continuing support as it implements its strategy," it said.Gibson, who was made a CBE in 1990 and knighted in 1999, said: "This term will take me into my eighth year on Wm Morrisons board, and this announcement gives the board time to conduct an orderly search for a new Chairman and ensure a smooth transition."The stock was down 0.5% at 192.8p after the statement on Thursday morning.BC