Huddle, the UK founded enterprise collaboration service, has raised $51 million to finance a large expansion.

Headquartered in San Francisco, Huddle is experiencing a boom in business and says the capital will help it grow at a faster rate. In 2014 it won seven of its top ten customers and business tripled from 2013.

Alastair Mitchell (above), CEO and co-founder, said, "Enterprises are frustrated with endless rounds of emails,  and are discovering how Huddle lets them collaborate internally, and with external partners, and to do it inside a secure environment."

The $51m adds to a total of nearly $90 million raised since its founding in November 2006.  It is one of the more successful businesses to emerge from London's "Silicon Roundabout" district, home to many European startups.

Techcrunch reporter Ingrid Lunden writes that the latest funding values Huddle at between $250m to $300m. This is a very humble valuation compared to the sky high valuations of many much younger Silicon Valley startups, some with no revenues or customers. 

From Alastair Mitchell's blog:

As we start on the next phase of Huddle's journey, it's also given me a chance to reflect and look back at how far we've come. From a bedroom-based start-up back in 2007 with a very small team - Andy [McLoughlin] and me - Huddle has grown exponentially. Today, we have 170 Huddlers based in four offices around the world - San Francisco, London, New York and Washington D.C.