The company, which opened its first site in King's Cross in 2007 and serves a tapas menu with Spanish wines and beers, has already earmarked its fourth site at Blackfriars, which it plans to open next spring.
Founders Richard Bigg and Nigel Foster said they were looking for more sites in the capital for the initial wave of expansion, which is expected to create an extra 250 jobs, but would not rule out taking the concept outside London if the opportunity arose.
Managing director Bigg said: "We want to bring the life and soul and tastes of Spain to more Londoners. We are delighted to be opening in the heart of the City, in Blackfriars, in spring 2013 and plan to open several more sites in the coming years.
"London is the initial starting point for further expansion, but we would love to bring Camino to a wider UK audience in future however."
Bigg said he and Foster, who have built a number of bar and restaurant businesses over the last 17 years, including Cargo and Cantaloupe in Shoreditch, had tried many different ways to secure funding in the past, including borrowing from the bank and selling businesses to release cash.
The pair started discussions with the BGF in the summer and agreed to let it take a minority stake in the business in exchange for the funding.
"BGF offered us a different option and we’re looking forward to working with them to bring Camino to a greater audience in London and the UK,” said Bigg.
BGF investment director, Alistair Brew, said Camino, whose annual turnover reached £6m at the end of November 2012, was 'one of the strongest leisure concepts' he had seen.
He said: "It’s responding to the current trend for social dining and stands out with its high level of Spanish authenticity. We welcome what is a great opportunity to support an exceptional management team and chairman in taking their business forward.
“There is no doubt that that many UK businesses have been affected by a tightening in consumer spending, but that doesn’t mean that good companies can’t prosper.
“Camino demonstrates that strong growth is possible for businesses with good ideas, strong management and ambition. It is these businesses that BGF is looking to back; and with up to £2.5bn available we are in a position to help.”
Camino opened its second site at Canary Wharf in 2010, following with a restaurant at Monument in 2012. The group also owns Britain's first dedicated sherry bar, Bar Pepito, which it opened at King's Cross in 2010.