UK fund manager Gartmore Group will be valued at about £800m (€876m) when it floats half of its shares next month in an initial public offering, producing a strong return for US private equity firm Hellman & Friedman and the company's fund managers, who bought Gartmore three and a half years ago for little more than half that.

According to a preliminary prospectus seen by Dow Jones Newswires, Gartmore expects to raise £280m in gross proceeds from the sale, while current shareholders will cash out about £120m in stock.