Facebook's top executive in Europe, Joanna Shields, is leaving to spearhead the government's scheme to create a 'Silicon Valley' cluster of technology businesses in East London.
Shields, who is vice-president and managing director of Facebook EMEA, is to become chief executive of the Tech City Investment Organisation in January.
The social network, which is also looking for its first UK managing director, does not have a replacement for her lined up yet.
At TCIO Shields will replace Eric van der Kleij, who did not renew his contract when it ended this summer. She will also take up a position with the government as ambassador for the Digital Industries.
Shields joined Facebook in 2010, after a brief period working at Elisabeth Murdoch's digital media media venture ShineVu. She made her name at the social network Bebo, where she was president. She oversaw the sale of the business to AOL for $850m (£417m), later becoming president of its social media divison.
Prior to her role at Bebo, Shields was managing director at Google, where she was responsible for building and managing the company's advertising and syndication network across Europe, Russia, the Middle East and Africa.
The Tech City Investment Organisation (TCIO) was set up by the government department of UK Trade and Investment in April last year, to support the growth of technology businesses in East London and make it the location of choice for tech and digital businesses.
Businesses that have set up offices in Tech City include Amazon, Google, Intel and Cisco. Shields’ role will involve helping to promote the area, raising its profile internationally, and attracting investment.