Shields has spent an equal amount of time in both cities (14 years each) and doesn’t pretend that London is the next Silicon Valley. London is composed of tech clusters across the city, each with its various strengths, rather than one large location where all entrepreneurs congregate. Such a cluster model brings together ­lawyers, accountants, bankers, and other professionals from the surrounding ecosystem, she said.

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Silicon Valley isn’t the only innovation hub, De Rycker added. “There’s a big difference between starting a company vs. getting to critical mass.” At that point, she said, entrepreneurs need to locate in an industry cluster ­that suits their needs. “People go to clusters for talent,” De Rycker continued. In Silicon Valley, there’s so much activity and so many potential employers for developers, that salary costs can quickly grow prohibitive. Also, enabling institutions ­like government, immigration policies, and access venture capital ­make several different cities appealing to different founders.

London aims to emulate Silicon Valley’s philosophy ­that success is not just a possibility but also a prerogative. Shields said she’s seen London entrepreneurs shift more towards that ethos. When she first moved abroad, her employees scoffed at stock options. They wanted pensions. She laughed, saying today that they all want to be the next Mark Zuckerberg.

Though everyone wants to found the next hot startup, De Rycker said that Silicon Valley’s undiluted obsession with tech is not necessarily the right recipe for other cities. That focus gives the Valley an edge, but she seemed wary of the sustainability of that model. (Though, she clarified, she is not saying Silicon Valley is dead.) Shields did applaud large American companies’ acquisitive nature, explaining that they look to entrepreneurs for innovation. “The energy that comes in with a new idea can completely transform a business and lead you on a new trajectory,” she explained, encouraging European companies to take notice of the small companies growing in London’s tech clusters.

London may have learned from America’s streak of entrepreneurial successes, but sometimes the Silicon Valley way doesn’t translate so well. Everson moved to London in January to search for Facebook’s next president of its European, Middle East, and Africa business. ­Shields stepped down from the position to head Tech City ­and was immediately surprised by the way the social network was perceived abroad. “Externally, we didn’t have a clear articulation of what Facebook meant for marketers,” she said. Clients told Everson that Facebook’s presentations weren’t humanizing, which led her to get in touch with Menlo Park and refocus the company’s branding. “There’s been a lot of work on the brand,” she told the audience, crediting her move to London with her changed approach.

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The Facebook exec then shared some of the best advice she’s ever received: When you walk into a room, think of yourself like a thermostat; dial it up and down as needed. As London’s presence in the tech world grows, it seems to be doing just that, taking only what it likes from the Silicon Valley model.