It was, by all accounts, a strange turn of events. Naomi Watts - the Australian actress who plays Princess Diana of Wales in Oliver Hirschbiegel's new biopic - walked out of an interview with movie critic Mark Kermode and the mild-mannered broadcaster Simon Mayo during the pair's BBC 5Live movie show this week.

Naomi WattsNaomi Watts Plays Princess Diana

Kermode is known for his formidably forthright opinions, though his interview subjects are usually treated to nothing less than a serious, intelligent discussion about whichever movie they're flogging at the time. See Kermode's chat with Ben Affleck during the promotion for Argo as a prime example. At the end of the discussion - filmed for the Culture Show - the American director was heard to say, "Nice interview," after presumably being swamped with the same predictable queries all day.

But it all appeared to be too much for Watts, who arrived in the BBC studio to chat about Diana, which follows the Princess's relationship with the heart surgeon Hasnat Khan, played here by Lost's Naveen Andrews. The film company said they set out to make an "insightful and compassionate study of Diana's later years," though there had been rumblings for months that this movie is very, very bad.

Though both Kermode and Mayo denied it, perhaps their probing about the ultimate success of the movie prompted Watts to walk out? The Oscar-nominee is an intelligent actress, if Diana is as bad as the critics are saying it is, than she will have known well before her chat with Britain's foremost movie critic. 

It was the tabloids that got the ball rolling - or the knife piercing - on Diana. 

The Mirror's David Edwards described the film as "a cheap and cheerless effort that looks like a Channel 5 mid-week matinee."

In a horrendous one-star review, the Daily Mail's Christopher Tookey called it "terribly, terribly dull," adding, "The movie is not as tacky or sensationalist as one might fear," before concluding "the bottom of the royal barrel has been scraped once too often."

But forget the royalists at The Mail - maybe the liberal minded broadsheets could find at least one redeeming feature with Diana? 

Peter Bradshaw of The Guardian didn't hold back. At all. 

"Poor Princess Diana. I hesitate to use the term "car crash cinema". But the awful truth is that, 16 years after that terrible day in 1997, she has died another awful death," he wrote, adding, "...the film creates a distorted, sugary and preposterous impression. She is the Heiress Of Sorrows."

Geoffrey McNabb of The Independent somewhat strangely opined, "Perhaps, Hirschbiegel could have made a stronger film if he hadn't been lumbered with the baggage that the real Diana brings," though as Bradshaw probably quite rightly suggested, "A good film could be made about Diana's dark side - that is, her flawed, non-saintly human side..An entire movie could be made, for example, about her ugly, obsessional spat with her sons' nanny Alexandra "Tiggy" Legge-Bourke, whom she suspected of having an affair with Charles and whom she publicly insulted. That really was dark."

Naomi Watts Princess DianaPrincess Diana, As Played by Naomi Watts. Do you see the resemblance?

Oh, and if you thought this was one of those "the great performance from the lead is overshadowed by a bad script" movies, than think again. Watts - whose performance in last year's The Impossible was Oscar-nominated - comes in for criticism too.

Bradshaw says "she looks like she's in a two-hour Spitting Image sketch, scripted by Jeffrey Archer."

The Mirror's Edwards says she "looks, acts and sounds nothing like the Princess of Wales," adding, "Wesley Snipes in a blonde wig would be more convincing" - which is not true at all.

Diana hit theaters in the UK on September 20, 2013.

Watch the Diana trailer: