Former US vice president and environmental activist Al Gore has invested £8 million in Ovo Energy through his sustainable investment fund.
Generation Investment Management, a fund established by Mr Gore back in 2004, was known to be in talks with the Bristol-based energy supplier late last year (2013).
A deal was agreed in January, however, an Ovo Energy spokesperson said it had only just been made public because founder, Stephen Fitzpatrick, "is just not that keen on self-promotion."
Rather than take a direct stake in the business, the investment is a mezzanine finance deal - a factor considered important by Mr Fitzpatrick.
Commenting on Generation Investment Management's investment, the founder stated: "The most important thing for us was that we didn't have to give up any control. We had previously turned down a deal with a private equity investor as we were being asked to give up too much control relative to the stake we were selling."
Mr Fitzpatrick added that the electricity and gas supplier had tripled in size in the past 12 months and that it wanted to go public on the stock market in order to raise more money.
Founded in 2008, Ovo Energy has seen both its customer and staff numbers increase considerably in the past 10 months. Its customer numbers have risen from 150,000 in October 2013 to around 400,000.
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