Allan Leighton, a former chief executive of the British supermarket group Asda-WalMart, has joined the board of Office, the successful British footwear retailer, as non-executive chairman. Office has 84 standalone stores in the U.K. and Ireland as well as 52 concessions in those countries and the U.S. It opened eight stores and eight concessions in 2011, and plans to open at least six more this year; Leighton was brought on board to help with the expansion.