Buffett started working life as a grocer but has just paid $1.5 billion for McLane grocery division, which distributes food to drugstores, convenience shops and 7-eleven chains across the US. It made sales of $14.9 billion last year.

Buffett will leave McLane's executive team in place and the company headquarters will stay in Texas.

Buffett began his working life at the Omaha grocery store run by his family for generations. When asked why he walked away from a job that paid 25 cents an hour and involved physical labour, the billionaire replied: 'It would have been undignified to run.'