LONDON--College Group, the fast-growing financial group that owns City PR heavyweight College Hill, has been sold to private equity firm Vitruvian Partners.

The deal sees Vitruvian Partners acquire a small majority of College Group’s equity. Chairman and largest shareholder Alex Sandberg told the Holmes Report that he and the group’s 130 employee shareholders had sold around half of their stakes.

Formed in 1990, College Hill has grown to reach almost £25 million in fee income in 2010, according to the 2011 Holmes Report Global Rankings, including double-digit growth in 2009 and 2010. The broader College Group, which includes employee engagement, brand consultancy, research, and digital, is worth approximately £40 million.

The deal values College Group at around £45 million and marks the first time that the firm has taken on an external shareholder.

“What we’ve done is to raise some capital,” Sandberg told the Holmes Report. “We’ve grown very fast over the last two years. I think our business model is well proven. To do what we want to do next, frankly, we need more capital than what we’ve got.”

Sandberg is hoping to use the new funds to spur greater geographic expansion. College Group currently has 13 offices worldwide, but only two (Hong Kong and Mumbai) in Asia, and a relatively small North American presence.

He also pointed out that, despite the deal, the firm has “retained its independence.”

“We will continue our geographic spread, and in turn that will bring us opportunities and businesses,” said Sandberg. “We are still independent - there are companies that want to be part of a global independent network.”

“We know Vitruvian because they are invested in a couple of our clients,” he added. “They are quite special because they are not frightened of people businesses that want to grow fast. They are also in London, and they are good people to deal with.”

Named the Holmes Report’s EMEA Financial Consultancy of the Year in 2010, College Hill has expanded rapidly over the past four years, tripling revenues, and acquiring numerous businesses. Pure financial communications, once the lion’s share of the firm’s business, now accounts for less than a quarter, with public affairs and broad corporate communications work contributing a larger share. In addition, more than a quarter of the firm’s clients are now using multiple practices, and a growing number are drawing on College Hill services in other markets.

The deal comes as financial firms look to bolster their cross-border capabilities, as evidenced by the recent merger of WPP companies RLM and Finsbury.