The actor reveals reporter Paul McMullan told him he had been hacked by a private investigator hired by the newspaper's bosses and he decided to investigate further after the police "did nothing" when he alerted them to the scandal earlier this year (11).
He met up with McMullan over a "few drinks" and quizzed him on what the hack insisted was "routine", while secretly taping the conversation.
That became the basis for an article Grant wrote for U.K. magazine New Statesman, which first brought the extent of the newspaper's sleazy practices to the public.
The actor tells Entertainment Weekly magazine, "That created quite a big stir."
And Grant admits he had no problems outing McMullan and secretly taping his boasts: "It felt like symmetry for sure. You know, they hacked me, I hacked him."
The Four Weddings And A Funeral star called for a full-scale investigation into the workings of the British tabloid newspaper industry in the days leading up to publishers' decision to close the News of the World amid the snooping scandal last week (ends08Jul11).
He joined a protest in London calling for a probe into the scandal and told Sky News, "We need an inquiry that uncovers all the practices and indeed culture, not just at the News of the World but of all tabloid journalism in this country because what we are going to find out over the next weeks and months is that this wasn't just at the News of the World."