G4S share price has fallen 9% as it struggles to deal with the fallout from the failure to provide adequate security personnel for the Olympics.
It admitted it could not provide 10,400 venue guards it had been contracted to deliver, costing the firm up to £50m.
The admission forced the British government to call up 3,500 extra troops and police as cover and has put pressure on company with 2011 revenues of £7.5 billion.
Running care homes and prisons, fighting pirates and mystery shopping, G4S was long in the background of many people's lives before its London Olympics debacle put the company in the middle of a media and political storm.
The G4S group is made up of a list of businesses that spans five continents and employs more than 657,000 staff, making it the world's second largest private sector employer behind U.S. retailer Wal-Mart and world's biggest the biggest security company.
The British group targeted London's Olympics as a flagship security deal that would put it on the map and help win new work at home and abroad.
The hostile headlines, made worse by Prime Minister David Cameron calling for G4S to face the consequences, have been a harsh wake-up call for a company that has been an active part of most people's lives for much longer than they realise.
In its core British market, the firm with the slogan "securing your world" has a hand in everything from airport security and immigration, to running prisons, police forces and cleaning and catering in schools and hospitals.
The group also trains British troops before deployment, handles the administration of penalty train fares, installs residential smart energy meters, runs children's homes and manages cash transportation for banks and retailers.
Around the world it protects embassies, manages more than 40,000 electronically tagged offenders, guards ports and airports as well as nuclear, oil, gas and mining sites, and even protects container ships from pirates off Africa and Malaysia.
Staff range from spotty teenagers directing crowds at events such as Wimbledon to former SAS soldiers and police specialists able to construct anti-kidnapping strategies or assist local police forces.
Government contracts amount to over half of the company's British revenue and the market makes up over 20% of its bid pipeline, including contracts to run seven prisons that will be awarded later this year.
Dealing in such high security areas means its work has not been without controversy. The group, which became a global giant in 2004 when Securicor merged with Danish company Group 4 Falck, which had had to deal with a number of prison riots and escapes before the merger.
Last year the firm left prisoners locked up for almost 24 hours at a Birmingham jail after losing the keys to cells, and in an other incident guards tagged a man's false leg, allowing him to remove it and break a court-imposed curfew.
G4S, whose shareholders' meetings are often attended by protest groups, faced criticism over the death in 2010 of Angolan deportee Jimmy Mubenga, who collapsed on a commercial flight from London's Heathrow Airport.
The problems have more recently spread to the boardroom. Last year G4S, which competes against rivals such as Securitas and Serco, felt the wrath of its investors when it caved in to pressure to scrap a planned £5.2 billion acquisition of Danish cleaning firm ISS.
The failed move, which required a £2 billion rights issue and would have seen the group become even larger with a push into the less controversial cleaning and catering sector, cost the firm around £50m in advisers' fees.
Chief Executive Nick Buckles, admired internally for his wide knowledge of every part of the business, had his strong credibility to thank for not losing his job, but some have warned his 27-year stay may not last much longer following the Olympics debacle.
Buckles' damage control efforts began at the weekend with a series of media interviews but had little effect on Monday, when G4S shares fell 9% on the London Stock Exchange.
While the weeks ahead will be a nervous time for Buckles, the blame may also fall on senior UK events management figures Mark Hamilton - who has worked as a bodyguard to Paul McCartney - and Ian Horseman Sewell, who just 10 days ago told Reuters G4S was confident it could run the Olympics Games and another similar-sized event elsewhere at the same time.
Buckles will face a British parliamentary committee hearing tomorrow to explain the Olympics fiasco, a meeting that could have some effect on the firm's ability to win new work in the crucial government sector.
