LONDON — On Dec. 21 last year, The Daily Telegraph was preparing to publish a blockbuster exclusive: Vince Cable, the government’s business secretary, had been caught on tape boasting that he had “declared war” on Rupert Murdoch and would find a convenient legal excuse to block the News Corporation’s bid for British Sky Broadcasting, Britain’s most lucrative satellite television network.

But the day before The Telegraph was to run the article, the paper was scooped by Robert Peston, the business editor of the BBC. Mr. Peston reported that “a whistle-blower” had provided him with a secretly recorded conversation between The Telegraph’s undercover reporters and Mr. Cable.

Senior editors at The Telegraph, furious that Mr. Peston had somehow beat them on their own story, suspected they were the victims of corporate espionage.

As the editors saw it, the person who stole the audiotape of Mr. Cable was either an enemy of the newspaper or someone with a motive to see Mr. Cable replaced by an official more willing to push forward the Murdochs’ bid for BSkyB, as the network is known.