As the blogosphere rubbishes the latest round of Batman casting rumours, fanboys are boiling at the prospect of Norbit's star obscuring their much-loved franchise. But the reporter who broke the story tells me he's sticking to his guns

Eddie Murphy has not had the easiest run of late. Box office bomb Meet Dave followed critical derision for Norbit. Ed was so upset at failing to secure the best supporting actor gong for his work in Dreamgirls at the 2007 Oscars that he upped and quit the ceremony.

But nothing could have prepared Murphy for the insults hurled his way after he was named yesterday by The Sun as the new Riddler in Christopher Nolan's follow-up to The Dark Knight. Fans of the fourth-highest grossing film of all time have been quick to express their revulsion at the thought of Murphy in the role, while commentators have angrily dismissed the story as "more bullshit casting stories".

"There is not one shred of reality in any of these rumours," wrote Harry Knowles of US film geek bible Aint It Cool News. "If ANY OF YOU believe any of this bullshit, you have found some crazy awesome drugs and I would like to have some of what you're having."

Yikes. Why such anger over a mere casting rumour? Well the ire has been building slowly following a similar piece in the Mirror in August which made the unlikely claim that Cher was going to play Catwoman in Nolan's new film. The Murphy rumour was, it seems, the straw that broke the Batman's back. The story in yesterday's Sun also didn't help itself by suggesting that Shia LaBeouf would play Robin in the new film: apart from anything else, Nolan's hyper-modern take on the caped crusader would seem to rule out the installation of a camp sidekick best remembered from the kooky 1950s TV show and Joel Schumacher's much-loathed 1996 effort, Batman and Robin.

The article was further undermined when Murphy's representative told TV show Access Hollywood it was categorically "not true". Meanwhile, Nolan stayed tight-lipped on the subject during a webchat with fans, in which the only vaguely notable revelation seemed to be that Heath Ledger improvised the Joker's clapping during the Dark Knight scene in which Jim Gordon is made police commissioner of Gotham.

But why pontificate on just how unlikely it is that Murphy will ever don The Riddler's question-mark-emblazoned emerald spandex, when you can go straight to the source? The Sun's Gordon Smart told me this morning that he was standing by his story on the basis that it had come from a reliable contact – one responsible in 2005 for revealing to the world the then-unlikely casting of Daniel Craig as 007.

"Everyone had a crack at us when we published that one," said Smart. "I was almost laughed out of conference that day, but it turned out to be spot on. I wish I had had a bet on it."

Off the record, Smart revealed his precise source, and if we are to believe him, it would appear a pretty reliable one. It follows, then, that the rest of yesterday's story might also be falsehood-free.

So, on that basis, prepare yourself for a Dark Knight sequel in 2010 (despite the fact that Nolan hasn't even officially signed on yet for a third film) titled Gotham, featuring Murphy, LaBeouf and Bale, with Rachel Weisz as Catwoman. Gird your loins, also, for a cliffhanger denouement in which Wayne Towers is hit by a blast which may or may not have offed the Batman.

Does that really, really appeal? Your thoughts below, please.