A chain of clinics famous for helping celebrities such as Paul Gascoigne overcome their addictions has been sold in a deal valuing the business at £875m.

Priory Group, which has more than 1,800 beds in 42 locations, has been sold by private equity firm Doughty Hanson, three years after it acquired the company.

Doughty, which has sold the business to banking group ABN Amro, is said to have made a return of at least four times its original equity stake. The size of Doughty's holding - and that of chief executive Chai Patel and other management - has not been disclosed.

Since the takeover in 2002, the group has added 11 sites and now includes 15 psychiatric hospitals, seven schools, two therapeutic community assessment services and five brain injury and rehabilitation units.

The portfolio includes two of the UK's oldest private mental health hospitals - at Roehampton and Ticehurst House near Wadhurst, East Sussex.

The group was founded in 1980 with the acquisition of the Roehampton site by Community Psychiatric Centres, a US company based in California.

Growth and further expansion of acute psychiatric hospitals in the 1980s and 1990s started with the acquisition of a site in Bromley, south east London, in 1983.

The current Priory group is the result of Dr Patel acquiring Priory Healthcare and merging it with the specialist healthcare services division of Westminster Health Care in 2000.

The Priory is best known for its celebrity guest list, which has included the singer Pete Doherty and ex-England footballer Paul Gascoigne.

ABN Amro is thought to have beaten off strong competition to win the auction, with venture capital groups Apax Partners, Cinven and Charterhouse among the other parties thought to be interested in the company.