Hugh Grant, in his time, has played many parts. He has been the diffident, floppy-haired charmer in Four Weddings And A Funeral; he's been the caddish lothario in the Bridget Jones movies and the troubled quasi-dad in Nick Hornby's About A Boy. Off-screen, he's been the sheepish bad boy caught in flagrante by the roadside in LA, but also the brilliant investor in property and contemporary art.

But now he's found what could be his greatest role. On BBC TV's Question Time, he was the campaigner for decent values and fearless scourge of the slimy News Corporation which hacked into people's phones and sacrificed 200 jobs to protect Rebekah Brooks. It was a magnificent performance – and TV watchers all over the country remembered why they loved Hugh Grant.

With elegance, with insouciance, Grant dismissed the whingey complaints from fellow panellist, Sun columnist Jon Gaunt. He suavely batted away jibes about blow jobs. He called Rupert Murdoch's act of corporate self-mutilation "cynical" and the studio audience applauded.

The Daily Mail columnist Jan Moir has jeered at "St Hugh of Grant", and Piers Morgan – a man whose moral compass directs him unerringly to that side of the bread where the butter is to be found – tweeted that Grant was "a screechy, sanctimonious little prick". He found himself un-followed in droves. Morgan discovered that people supported Grant. And they wondered if being screechy and sanctimonious was a wise subject for Morgan to be talking about.

Grant had already shown remarkable flair and boldness in uncovering hacking, making secret tape recordings for the New Statesman. His detestation for the tabs and the paps is well known, and has occasionally sounded petulant on the subject. But the Hacked Off campaign had brought out in him a new authority: in interviews, he has even, emolliently, conceded that the general public were not too sympathetic about publicity-hungry celebs getting hacked, but Milly Dowler was a different matter entirely.

How has Grant emerged as the scourge of News International? I think it is because he, unlike everyone else, really doesn't care about the whole silly showbiz carousel and could step off any time he liked. Perhaps that is what he is doing now. Very often he had given the impression that he wouldn't be fussed if he never made another movie ever again. Plenty of stars hate Murdoch's papers, but they want to appear in movies made by Murdoch's Fox group, and to work with people who are similarly in awe of the great potentate's tentacular reach.

Grant is different. He is now rich and successful enough – and perhaps simply unconcerned enough – not to care. He is the unruffled David Gower of the cinema – and campaigning. And his new role as the Hammer Of Rupe is just so unlikely that it commands attention.

This is a great new career direction for him. I say: bravo Hugh!