Seven private companies are bidding to take over contracts worth £2bn to run nine prisons in England and Wales for the next 15 years, in what has been described as the largest single privatisation in the UK's prison service to date.

In addition to private prison giants GEO and G4S, companies in the bidding include Sodexo, the French catering facilities company; Interserve, which specialises in support services and construction; Mitie, a facilities management and property services company that also runs Campsfield detention centre; and road maintenance outfit Amey, which is owned by Ferrovial, the Spanish group that runs Heathrow airport.

While some of these companies, like Interserve and Mitie, have never run prisons before (Mitie is in the immigration detention business, though), others, like GEO and G4S, have long experience and horrendous track records in the sector: GEO runs 116 detention centres in South Africa, Australia, the US and the UK; and G4S runs several prisons and detention centres in the UK and Israel, as well as detainee and prisoner escort services.