The Guardian journalist who worked with US whistleblower Edward Snowden on a string of security services exposes has announced he is to part from the newspaper.
Glenn Greenwald, whose partner David Miranda was detained at Heathrow airport this summer under anti-terror laws, said he is "incredibly proud" of what he achieved with the broadsheet.
In a statement published online he said news of his departure was leaked and he is not yet prepared to reveal the "dream opportunity" he is leaving for.
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"My partnership with the Guardian has been extremely fruitful and fulfilling: I have high regard for the editors and journalists with whom I worked and am incredibly proud of what we achieved, " it read.
"The decision to leave was not an easy one, but I was presented with a once-in-a-career dream journalistic opportunity that no journalist could possibly decline.
"Because this news leaked before we were prepared to announce it, I'm not yet able to provide any details of this momentous new venture, but it will be unveiled very shortly."
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Since June Mr Greenwald, an American who lives in Brazil, has written a series of stories revealing internet and phone surveillance by US intelligence across the world, based on documents seen by former US National Security Agency contractor Mr Snowden.
The newspaper also published stories about blanket electronic surveillance by Britain's eavesdropping centre GCHQ.
In August Mr Miranda was held at Heathrow for nine hours when he changed planes on a journey from Berlin to his home in Brazil and police seized electronic items.
Alan Rusbridger, editor in chief of Guardian Newspapers, tweeted: "Sorry to be losing @ggreenwald after some thunderous reporting w @guardian. His new venture sounds +extremely+ interesting."
The Guardian's Jennifer Lindauer said in a statement: "Glenn Greenwald is a remarkable journalist and it has been fantastic working with him. Our work together over the last year has demonstrated the crucial role that responsible investigative journalism can play in holding those in power to account.
"We are of course disappointed by Glenn's decision to move on, but can appreciate the attraction of the new role he has been offered. We wish him all the best."