If you want proof positive of the extremely healthy returns still on offer from private equity, then look no further than today's deal for The Priory, the detoxification and stress-busting clinic that has extended understanding welcomes to celebrities such as Kate Moss, Robbie Williams and Paul Gascoigne.

Doughty Hanson, the private equity owner of The Priory since 2002, has offloaded the famous counsellor to surprise auction winner ABN Amro, the Dutch bank, for £875 million.

ABN appears to have booked its appointment at The Priory at the very last minute, but nevertheless managed to outmanoeuvre rival bidders Fortress Investment Group, the American hedge fund, and private equity rivals BC Partners, Cinven, Charterhouse and Electra.

Another consortium, Barchester Healthcare, backed by Irish racing tycoons John Magnier and JP McManus, was reported to have retired earlier, feeling a little out of sorts about the price.

And in the end that price looks potentially headache inducing, coming in a chunky £225 million higher than the £650 million that The Priory was originally expected to fetch.

As well as realising millions of pounds in profits for Dr Chaitanya Patel, the chief clinician who has a stake in The Priory, the sale will also see Doughty make an extremely profitable exit from its investment.

Doughty invested £116 million of its own equity buying The Priory three years ago. The total original sale price was £306 million, as £190 million of debt was involved.

Selling out for an enterprise value of £875 million today means Doughty has made five times its original equity investment in three years - a perfectly respectable period for a private equity company to stick with an investment, although the lead time for exits appears to be shrinking by the day.

This is not bad for a company like The Priory, which last year reported turnover of a pretty modest £155 million.

The Priory is now Britain's leading independent provider of private mental healthcare services, operating more than 1,700 beds across a network of 40 sites, including, of course, its clinic in Roehampton so popular with stressed celebs and the paparazzo.

And Doughty has built up the business, adding 11 additional sites and increasing the number of beds on offer by nearly 700 - to 1,833 from 1,148. It has also brought in new management, in the shape of finance director Paul Greensmith, chief operating officer Mark Beadle, Stephen Bradshaw, director of schools, and Chris Thompson, director of healthcare.

Sales since the acquisition have grown at a compound annual rate of 14 per cent.

What ABN Amro will do with The Priory is not entirely clear. But one thing is certain: private equity loves investing in healthcare providers and has been snapping them up at a gallop for the past two years - the cashflows are strong, and people will always get ill and need to be treated.

You can't help but wonder whether Doughty Hanson explored the flotation route when it decided it wanted to check out of its investment. If it did, and found only weak interest among the share-buying community, is this yet another example of private equity making the public markets look woefully slow on their feet?

Perhaps a visit to a place where they can relax, take their mind off things ...

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