The reason? It shows Luke Skywalker (Mark Hamill) back on board the Millennium Falcon, the "fastest hunk of junk in the galaxy", as it was once called.

Luke was last aboard the ship - in rather bad shape, having lost a hand to the Dark Lord of the Sith who had just revealed himself as his father - at the end of The Empire Strikes Back in 1980. This time he looks to be in fuller command of his faculties, even if his mood is still rather bleak.

This is the third trailer released for the eighth Star Wars film, which opens on December 15, and it continues to develop the central theme evident in the previous two: light and dark striving to assert dominance, or alternatively to come into balance.

Adam Driver's Kylo Ren, the new villain of the series, reprises a line we've heard before. "Let the past die," he says. "That's the only way to become what you were meant to be."

We don't yet know whom he is addressing, but it's a fair bet it's Rey (Daisy Ridley), who seems to occupy the space in this saga that was occupied by Luke in the first trilogy, a neophyte Jedi knight torn between wanting to do the right thing and giving full rein to her power whatever the cost.

That theme gets a further echo in the words of Supreme Leader Snoke (Andy Serkis), whom we saw in The Force Awakens only as a giant holograph but who was revealed in the second trailer in his full disfigured glory. "Darkness rises and light to meet it," he growls ominously.

Little wonder, really, poor Rey seems so confused. "I need someone to show me my place in all this," she says.

The notion of inversion gets another airing in the appearance of John Boyega's Finn. Having shed his Stormtrooper origins to join the Rebels in The Force Awakens, here he is in the uniform of an Imperial officer. Has he switched sides again? Not likely, as he's doing battle - with a light sabre, no less - with Captain Phasma (Gwendoline Christie) who is, despite her gleaming silver armour, on the side of darkness.

How will all this play out? Who will survive? Who will join the Dark Side? Who knows.

Mark Hamill has teased his followers with a clue - or, more likely, a bit of misdirection - over on Twitter.

With Luke having already appeared in the looming Darth Vader position on a poster for the film some months back, a new poster for the Japanese market shows Rey in that same spot.

"Hey you Dark Side theorists: Look who's looming at the back of the poster now," Hamill tweeted. "Another clue for you all... #TheWalrusWasPaul " he added, a reference to the theory that there were clues to the "fact" Paul McCartney was dead on the cover of the Beatles 1969 album Abbey Road. Of course, he wasn't, unless that's a hologram currently touring the world.

The trailer ends with Rey looming over Luke in the pouring rain, light sabre at the ready and seemingly poised to strike. But it's Luke's voice we hear.

"This is not going to go the way you think," he says.

That's probably the only thing we can take as gospel.

Facebook: karlquinnjournalist Twitter: @karlkwin Podcast: The Clappers