I, TONYA (15, 119 mins)

Starring: Margot Robbie, Sebastian Stan, Allison Janney, Julianne Nicholson, Paul Walter Hauser, Bobby Cannavale, Caitlin Carver. Director: Craig Gillespie.

According to a title card at the beginning of Craig Gillespie's blackly humorous biopic, I, Tonya is based on "irony free, wildly contradictory, totally true interviews" with US figure skating champion Tonya Harding and her ex-husband Jeff Gillooly.

The film illuminates a grubby episode in sporting history - the 1994 attack on skater Nancy Kerrigan - with considerable aplomb.

Screenwriter Steven Rogers invites the deeply flawed protagonists to talk directly to camera, offering contradictory and overlapping testimonies that make sense of the chain of events that led to Harding's ban from competitive skating.

Margot Robbie inhabits the title role with fearlessness and ferocity, tossing out expletives as if her life depended upon it as Harding suffers grievously at the hands of those closest to her.

Sebastian Stan oozes slippery charm as the man who walks Tonya down the aisle and exerts his marital "right" to lay his hands on her in anger.

Scenes of domestic abuse are extremely upsetting and Gillespie pulls no punches in his depiction of the couple's volatile, self-destructive relationship.

As a young girl, Tonya (Robbie) learns to ice-skate at the behest of her domineering mother LaVona (Allison Janney), who secures Diane Rawlinson (Julianne Nicholson) as a coach for her daughter.

LaVona is far from impressed with Jeff (Stan) as a potential son-in-law - "Marrying the first idiot who said you're pretty," she snarls - but she is powerless to stop Tonya from falling under Jeff's spell.

He is particularly flattering about her abilities on the ice.

"It's like your superpower," he coos, lavishing Tonya with the kind of compliments that have been all too rare.

She trains hard and becomes the first American athlete to land a triple axel jump in competition but judges refuse to give Tonya the high marks she thinks she deserves.

In stark contrast, rival Nancy Kerrigan (Caitlin Carver) is lavished with praise and repeatedly overshadows Tonya's achievements.

As frustration grows, Tonya's bodyguard Shawn Eckhardt (Paul Walter Hauser) and Jeff hatch a loopy plan to hire two low-level criminals to attack Kerrigan after one of her practice sessions.

I, Tonya is a barbed satire across the class divide, anchored by tour-de-force performances from Robbie and Janney, the latter monstrous as a chain-smoking matriarch, who preaches cruelty as kindness to jaw-dropping excess.

Sequences on the ice are breathlessly staged, employing slick digital effects to blend Robbie's face with the bodies of skating doubles so we truly believe the Australian actress is recreating the intricate routines.

"That's the story of my life," growls Tonya in the film's blood-spattered closing moments, promising us that she has told us the unvarnished truth.

Whether we believe her or not, she recounts a cracking yarn of triumph against adversity. 8/10