THE world's richest man and the world's biggest security company are working on the same team.

Bill Gates, the Microsoft founder and philanthropist, has been revealed as an investor in G4S, with a stake of more than 3 per cent.

G4S was the security company accused of bungling security at the 2012 London Olympics.

The investment is divided between the charity run by him and his wife, the Bill and Melinda Gates Foundation, and his asset management firm Cascade Investment.

The security giant is working to restore its reputation after its chief executive, Nick Buckles, quit last month after a profits warning that saw shares in G4S plummet nearly 15 per cent in one day - the latest in a string of embarrassments.

Before last year's Olympics fiasco, when a failure to provide enough staff resulted in the Army having to be called in, angry shareholders forced the abandonment of a £5.2bn takeover of the Danish cleaning group ISS in 2011.

With G4S announcing yesterday that Mr Gates' stake had risen to 3.2 per cent by the purchase last week of some 6 million shares, a spokesman for the company said a meeting between the two parties would be arranged.

The shares purchase is a vote of confidence in the company and a boost for Ashley Almanza, who has not had a quiet start since becoming chief executive on 1 June. G4S's annual meeting last week was disrupted by protesters angry over Jimmy Mubenga, an Angolan who died while being deported from the UK by G4S guards. More than 20 per cent of shareholders also voted against executive pay at the AGM.

Other UK investments held by Mr Gates include the Guinness brewer Diageo, and retailer Carpetright.

However, shares in G4S, which have dropped more than a fifth since April, failed to rise on the news, closing 1.8p lower at 242.8p.