Description:It's been a troublesome few months for the world's third largest retailer. In January Tesco issued a profit warning, their share value has gone down 18 percent and market share has fallen to levels not seen since 2005. Now, the firm says it's UK chief executive, Richard Brasher, will be quitting his post after less than a year. The group CEO, Philip Clarke says he'll take on the UK role.(1:28)