Tom Watson is a little bleary but otherwise in good spirits. Exposing the dark heart of the world's most powerful news corporations is physically demanding, black coffee-fuelled, exhilarating work; he doesn't always get eight hours sleep. In fact, for the past three weeks, the 44-year-old scourge of Rupert Murdoch has averaged three hours a night as he gives TV interviews, writes letters to Scotland Yard, asks Commons questions and generally causes havoc to Mr Murdoch's hopes of continuing in business in Britain.
The two-year campaign by the Labour MP for West Bromwich East to uncover the scale of wrongdoing at Mr Murdoch's News International (NI) dramatically burst to life three weeks ago with the disclosure that its best-selling paper, the News of the World, had hacked into the mobile phone of Milly Dowler.
The ensuing "firestorm" (David Cameron's words) forced the Prime Minister to open a public inquiry and Rupert Murdoch to abandon the tabloid and, eventually, that other redtop he had been hoping to keep, NI's chief executive Rebekah Brooks.
At every stage, Watson has popped up on TV, newspaper front pages and Twitter undermining the PR counter-offensive from Britain's biggest newspaper group. He has also kept up the pressure in Parliament, where last week, as the resident phone-hacking expert on the Culture, Media and Sport Select Committee, he came face to face with the Murdoch clan: Rupert and James, and their former British chief, Ms Brooks.
As he waits for his lunch at a Mexican restaurant in Fulham, Watson pauses as he works out how to sum up the last few extraordinary weeks. "It has seemed like surfing a giant wave for two weeks solid," he says. "I've not been able to look down, nor take it all in."
His newfound fame has won him the admiration of assorted showbusiness stars. The strangest experience, he says, was George Michael calling him his hero, and he also had his hand shaken effusively last week by the comedian David Walliams, who stopped him on London's South Bank.
Despite the tumultuous events of the past weeks, he believes the "phone-hacking scandal" still has a long way to go. "I don't think we're half way through it," he says. "We're a lot closer to the people at the core of the organisation who really run News International; we're a lot closer to finding out who knew what. But as to the actual number of victims and types of criminal invasions of privacy, I don't think we're anywhere near to getting that story out yet."
Before he became known for his role in covering the scandal, Watson was a leader of the "Curry House plot" to unseat Tony Blair in 2006, for whom he was a defence minister. Gordon Brown made him a minister in 2008, putting him in charge of modernisation at the Cabinet Office.
He has an interest in technology and was one of the first MPs to blog and use Twitter. "I think the story might not have come about had not people using social media expressed their outrage. Certainly without Facebook or Twitter a consumer boycott of the advertisers of the News of the World would not have been organised so quickly."
Watson adds: "Even more embarrassing the editor of a website called Labour List is running a campaign for me to carry the Olympic torch which would" – the rotund MP laughs – "actually be the ugliest image in sporting history."