FROZEN II (U) Four stars

According to lovable snowman Olaf (voiced by Josh Gad), who is a permafrosted font of wisdom about the natural world, water has memory. Considering that audiences who flocked to the original Frozen are largely made of water, it’s safe to assume that their memories of Chris Buck and Jennifer Lee’s Oscar-winning adventure will ebb and flow throughout this visually stunning sequel to the highest-grossing animated film of all time.

Water and the other classical elements - air, earth and fire - play pivotal roles in Frozen II. The realistic movement of aqua has always been a chink in the armour of computer animators.

Not so here.

Disney’s platoons of digital wizards repeatedly quench our thirst with jaw-dropping set pieces including a thrilling gallop over crashing waves of an angry sea astride an untamed water horse.

We’ve had six years to commit to memory every note, key change and lyrical flip of Do You Want To Build A Snowman?, For The First Time In Forever, Love Is An Open Door and Let It Go.

It would be churlish to expect returning songwriters Kristen Anderson-Lopez and Robert Lopez to ride the crest of those sound waves again on a first listen.

In the sequel, Elsa’s call to arms Into The Unknown soars to dizzying high notes and Kristoff’s faux 1990s rock ballad Lost In The Woods is a hoot, replete with four-legged backing singers.

Anna’s solo The Next Right Thing is a beautifully melancholic distillation of grief.

Three years have passed since Elsa (Idina Menzel) ascended the throne of Arendelle.

An ethereal voice from the enchanted forest beckons her to unlock the secret of a bedtime story told to Elsa and sister Anna (Kristen Bell) by their parents, King Agarr (Alfred Molina) and Queen Iduna (Evan Rachel Wood).

“The truth must be found. Without it, there is no future,” confirms troll king Grand Pabbie (Ciaran Hinds).

Thus, Elsa, Anna and her goofy beau Kristoff (Jonathan Groff), reindeer Sven and Olaf journey to an ancient stone circle shrouded in swirling mist, which designates a hidden pathway to the supposedly lost Northuldra tribe.

Frozen II dilutes a conventional quest storyline to wring out the running time to 103 minutes. Inveterate scene-stealer Olaf hysterically recaps the first film in the sequel’s crowd-pleasing showpiece and finds a perfect match for his gosh-darn cuteness in a blue salamander sidekick.

While the first film encouraged characters to let go of things that hurt or hinder - fear, self-doubt, regret, the past - Buck and Lee’s follow-up dives deeper into their tearful self-reflection.

Menzel and Bell gently tug heartstrings as sisterly bonds strain and their brave heroines make sacrifices to remedy a great injustice.

“I’ve had my adventure/I don’t need something new,” defiantly trills Elsa.

Legions of fans do, and, despite its flimsy plot, Frozen II largely delivers.

21 BRIDGES (15) Three stars

Opportunistic thieves are in the wrong place at the wrong time, sparking a night-time police manhunt through the streets of Manhattan, in Brian Kirk’s propulsive action thriller.

Screenwriters Adam Mervis and Matthew Michael Carnahan milk droplets of dramatic tension from their simple and efficient set-up, running a stopwatch on the frenetic gun fights and car chases from the moment the lead investigating officer reminds colleagues, “If we don’t catch these guys in the next three to four hours, they vanish.”

On-screen time checks cleanly convey the relentless passage of time from the first pull of a trigger to the cacophony of a bullet-riddled final reckoning that poses uncomfortable questions about the fractious relationship between taxpayers and the people entrusted to protect them.

Chadwick Boseman trades Black Panther’s figure-hugging Vibranium weave mesh suit for more simple, functional attire as a morally incorruptible NYPD detective, who has been raised to never shy away from doing the right thing.

He is often the fulcrum of impeccably staged action sequences including a breathless pursuit on foot through the Subway transit system. Northern Irish director Kirk is a willing accomplice to explosive skirmishes beneath the gleaming glass and metal of a cityscape that never sleeps. With a sleek 99-minute running time, there’s no time for us to slumber.

HARRIET (12A) Three stars

The biggest surprise about writer-director Kasi Lemmons’s biopic of crusading abolitionist Harriet Tubman is that it has taken Hollywood so long to immortalise the 19th-century African-American trailblazer.

Born into slavery in Maryland as Araminta Ross, Tubman personally shepherded fellow slaves across the border to safety, served as a spy for the Union Army and remains one of the only women to lead an armed expedition on American soil.

Scripted by Lemmons and co-writer Gregory Allen Howard, Harriet romanticises the lead character on a pristine surface level, relying on a barnstorming lead performance from London-born Cynthia Erivo to atone for a sinful lack of character development.

Supporting players are reduced to historical footnotes, portrayed vividly by an esteemed ensemble cast including Tony Award-winning Hamilton star Leslie Odom Jr, Janelle Monae and Clarke Peters.

Tears course down their cheeks more readily than ours.

BLUE STORY (15) Three stars

South London-born rapper-turned-YouTube star Andrew Onwubolu aka Rapman makes his feature film directorial debut with an urgent cautionary tale about the futility of gang warfare on the streets of the capital.

He draws inspiration from newspaper headlines and his childhood in Lewisham to expand on themes from a semi-autobiographical trilogy of shorts also entitled Blue Story and openly question the sense of youths laying lives on the line based on something as arbitrary as the postcode of their council estate.

Rapman appears periodically on screen as a swaggering Greek chorus, underscoring a timely central message of cool heads under fire with lyrical narration.

“RIP to all the innocent lives/I hope these young ‘uns wake up and they start seeing the light,” he pleads aloud.

Stripped bare of the musical interjections, Rapman’s film follows a predictable trajectory from brotherhood to

bloodshed, employing a Romeo and

Juliet-style forbidden romance as the catalyst for enmity and petrol-doused retribution.