In May this year, a huge company listed on the London Stock Exchange found itself in the midst of controversy about a prison it runs for the government - Thameside, a newly built jail ... in south-east London. Two months later, the same company was the subject of a high- profile report published by the House Of Commons. Again, the verdict was damning: data had been falsified, national standards had not been met, there was a culture of "lying and cheating", and the service offered to the public was simply "not good enough". Three weeks ago, there came grimmer news. The company ... was one of two contractors that had somehow overcharged the government for its services, possibly by as much as 50m; The firm that links these three stories together is Serco. Its range of activities, here and abroad, is truly mind-boggling. As a private firm it's not open to Freedom of Information requests, so looking into the details of what it does is fraught with difficulty. But the basic facts are plain enough. As well as five British prisons and the tags attached to over 8,000 English and Welsh offenders, Serco sees to two immigration removal centres. You'll also see its logo on the Docklands Light Railway and Woolwich ferry. But even this is only a fraction of the story. Serco is responsible for air traffic control in the United Arab Emirates, parking-meter services in Chicago, driving tests in Ontario, and an immigration detention centre on Christmas Island.