The supermarket is clearly desperate: on Friday it issued a profit warning saying it expected full-year profits to hit £2.4bn, rather than the £2.8bn expected. The company has been battling against the increasing might of discounters Aldi and Lidl, whose market shares are slowly increasing.
How difficult will Lewis' job be? Formerly Unilever's president of personal care (and known as the "Dove man"), Lewis' management style is said to be more relaxed than that of Philip Clarke, Tesco's previous chief executive. But turning around Tesco's supertanker, which is currently on a collision course with a discounter-shaped iceberg, is going to take more than just charisma. Here are the biggest challenges he faces: