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Tech City could be a challenge to Silicon Valley, says PM

10 November 2011 Last updated at 16:17 GMT

The prime minister has unveiled an interactive map of East London's technology cluster, revealing more than 600 firms in the area.

The Tech City map highlights the expansion of Old Street's "silicon roundabout". By comparison there were around 200 tech firms based there last year.

The government said it was acting to support the area's success.

The BBC's Rory Cellan-Jones spoke to David Cameron about the progress being made in turning the area into a technology hub to rival Silicon Valley.