A former Tesco boss has been appointed to the top job at Guinness-owner Diageo, as the biggest drinks firm in the world seeks to turnaround its flagging sales.

Sir Dave Lewis will take over the brewing giant on 1 January, after former chief executive Debra Crew quit in the summer after two years in charge.

The firm has been battling weaker sales across its range despite a growth in Guinness sales, with shares recently falling to a 10-year low.

Following the announcement of Sir Dave's appointment on Monday, Diageo's share price rose 7% in early trading.

Diageo owns well-known brands including Johnnie Walker whisky, Smirnoff vodka and Captain Morgan rum, but has seen sales falling in key markets, in particular the US and China.