When Janine Gibson, the editor in chief of The Guardian’s Web site in the United States, realized that one of her columnists had a scoop about secret National Security Agency surveillance — potentially one of the biggest leaks in American intelligence history — she presented it to The Guardian’s top editor in London with classic British understatement.

“I’ve got a little story to chat to you about,” she told the editor, Alan Rusbridger.

Last week’s revelations about the extent of N.S.A. surveillance both in the United States and abroad is a major coup for the British news organization, which established a beachhead here less than two years ago. Mr. Rusbridger, who flew to New York from London last Wednesday in anticipation of the scoop, credits the story to the fact that The Guardian continues to invest in journalism when many news organization have cut back.

“We’re internationally engaged,” Mr. Rusbridger said Monday as he sat with Ms. Gibson in The Guardian’s conference room in Manhattan after a nonstop weekend. Outside the conference room, television screens featured reports from a range of networks, all focused on The Guardian’s story.

The scoop may also owe a partial debt to The Guardian’s longstanding liberal and anti-establishment approach to journalism. The newspaper has in recent years aggressively covered, among other stories, the News Corporation hacking scandal, the accusations of sexual abuse against the BBC personality Jimmy Savile, and the WikiLeaks release of diplomatic cables.