Tesco chief executive Sir Terry Leahy is to retire next March with Philip Clarke moving up to take his place as CEO at the UK's top supermarket chain.Leahy steps down after 14 years in the top job, a period that has seen Tesco become the dominant force in UK grocery retailing and start to make significant inroads into overseas markets in Asia and more recently the US. He will leave when he reaches 55."When I became CEO I had a plan to build Tesco around its customers, to make it number one in the UK and to find new long term growth in non-food, in services and in international expansion. I wanted to develop a purpose and values that could sustain Tesco through its challenges and encourage and grow future leaders. It has taken 14 years but that strategy has become a firm reality now and so I feel my work is almost complete," Sir Terry said. "Terry has made an unrivalled contribution over a prolonged period. He is undoubtedly one of the leading businessmen of his generation. He has put in place a strategy which can secure the progress of Tesco for years to come," David Reid, chairman, added.Clarke, 50, has come through the ranks at Tesco and joined the board in in 1998. Currently he has responsibility for the group's international operations in Asia and Europe as well as group IT.He first worked for Tesco in 1974 as a part-time assistant and joined the management training scheme after university. He has worked his way up as a store manager, a buyer, a marketeer and as an international executive.In a series of other boardroom changes, Tim Mason, president and CEO of the Fresh & Easy business in the US, will also become deputy chief executive, though still be based in the US. David Potts will become the first CEO of the Asia business, moving up from Retail and Logistics Director in the UK. Richard Brasher, currently Commercial Director, will be the CEO of the UK business and take responsibility for the Republic of Ireland.