You probably reckon Joaquin Phoenix's greasy, frayed take on the Joker is the most important part of the Joker trailer. That's fair enough. The film's called Joker, isn't it? It's about the Joker. Phoenix hogs the screen time. It's all about him, isn't it?

Well, no. You've probably missed the main man. At a minute and 54 seconds, we get a glimpse of Robert De Niro as a dancing talk show host. He's gone in a couple of seconds, but it's an important couple of seconds. Given how steeped in De Niro lore the Joker trailer is, his presence feels very pointed indeed.

preview for Joaquin Phoenix stars in Joker's first trailer (Warner Bros)

De Niro's canon of volcanic outsiders casts a long shadow. Obviously we've only got a couple of minutes to go on, but it says a lot that the couple of minutes we've been teased with contain huge dollops of De Niro's most potent anti-heroes. Phoenix's Joker looks like he's pulling from the self-loathing of Travis Bickle from Taxi Driver and the violent delusions - and failed stand-up career - of Rupert Pupkin from The King of Comedy. On top of that, this Gotham City looks a lot like the grotty, graffiti-streaked New York Bickle and Pupkin would recognise. On top of that, Martin Scorsese was an exec producer early on in proceedings before jumping ship because he was too busy.

Let's be honest, there's a lot of The King of Comedy here, specifically in the collision of glitz and grime and an arc which (going on this teaser, at any rate) follows a man who comes to live in his fantasies because he cannot bear the brutality and failure he sees around and inside himself. That's a classic De Niro trope: think of Jake LaMotta chuntering "I'm the boss, I'm the boss, I'm the boss...", Pupkin breaking into his hero's house to pretend he's popped by for a visit, or Bickle screaming at his own reflection. Most of all, Phoenix' Joker looks like he'll swerve the operatic but fundamentally mysterious evil of Heath Ledger's Joker and instead draw on the more brittle, unstable kind of menace De Niro channeled regularly in his pomp.

Yes, alright, we've only got two and a bit minutes to go on. But those two minutes show that this is unlikely to be much like any of the comic book adaptations we've seen so far. De Niro's presence sets the seal on the sense that this is a Scorsese-esque dive into a troubled mind on the fringes of an unravelling and unforgiving society.

Now, depending on your viewpoint, chucking De Niro in there is either a means of adding some gravitas and a sense of cinematic dynasty to Joker - of tying it definitively to those Scorsese-De Niro classics and their unique texture - or exactly the kind of on-the-nose move you'd hope a Scorsese-influenced psychological drama would avoid.

Either way, it's definitely ramped up the hype.