Some thought Joker, a violent comic book saga for grown-ups, would incite riots; others were worried its angular tale of a put-upon comedian who finally snaps, might inspire copycat crimes.

The film did no such thing. It did, however, make a billion dollars. It also won a couple of Oscars, and the suits at Warner were always going to want a sequel.

They might not have expected Phillips to make a musical. Some of our star performers are, it seems, reluctant to use the ‘M’ word while promoting the project. Lady Gaga, the film’s hard-working co-headliner, flat out refuses to describe it as a musical, and the trailer does its best to hide the singing bits.

It is as if everyone involved is afraid of what all that jazz will do to the profits. They shouldn’t be. Good or bad, Joker: Folie à Deux will make a fortune, and this strange and extravagant presentation goes about its business in a way that, say, the folks at Marvel would never allow.

In other words, it takes risks. To hell with comic book sources – this peculiar little film moves to its own beat. You want to see the Clown Prince take on Batman? Find another DC sequel. You want to see some action? Revisit the first film. With Joker: Folie à Deux, Phillips doubles down on the artful, experimental flourishes of its acclaimed predecessor.

He and his team build an edgy and eccentric song-and-dance show around a routine courtroom drama. A decent starting point, perhaps, but a solid concept is one thing – a killer follow-through is another, and this baggy, bloated follow-up struggles to fulfil its potential.

​We begin with Brendan Gleeson. Who better than a tough-talking Dubliner to put manners on Arthur Fleck/Joker (Joaquin Phoenix), the maniacal performance clown who murdered a beloved broadcaster on live television. Fleck is awaiting trial for his crimes, and Gleeson is the nasty guard at Arkham Asylum who keeps an eye on him.

It’s been two years since the events of the first film and, in that time, the Joker appears to have developed quite the fan base. Enter Lady Gaga’s Harleen ‘Lee’ Quinzel, a fellow inmate who randomly catches his eye. Lee is obsessed with the clown – Fleck falls head over heels. Anyone who knows their Gotham City villains will tell you where this relationship is headed.

Fleck’s careful, committed lawyer (Catherine Keener), all too aware of a possible death penalty sentence, is keen to clean up his image. Meanwhile, a slippery television personality (Steve Coogan), has other plans. Throw in a selection of well-oiled show tunes (That’s Entertainment, If My Friends Could See Me Now, Get Happy) and some chewy courtroom stand-offs, and you have yourself a bonkers set-up.

The big question is this: does Joker: Folie à Deux work? Not really. As a jaunty jukebox musical with a twist, it never quite finds its feet, or its purpose. As a drama, it feels drawn out, incomplete, and annoyingly unsure of itself.

We get it: Fleck is wrapped up in his own world, his own fantasies, and he imagines himself as the star of his own show. But he also breaks into song in the ‘real world’ and everyone is fine with that. You can’t have it both ways.

Phoenix was sensational in the first film, but to see him play the Joker again is like watching a magician perform the same trick twice: you appreciate the skill, but there are no more surprises.

Ms Gaga, then, is presented with an impossible task. Her Harley Quinn feels like an afterthought, something to distract us from all the stuffy courtroom chat. Gaga, who could never be accused of phoning it in, triumphs over Phoenix in the vocal department, but her dramatic work here feels flat and uninspired. It isn’t entirely her fault.

There isn’t an ounce of chemistry between our leads, and this shaky sequel spends most of its time dancing around in circles. A whole lot of nothing, basically.

Two stars