It’s difficult not to stare at Jack Black and Angelina Jolie because it’s hard to imagine a more discordant pair.

Jolie, a regular on most beautiful lists who shines on screen in femme fatale roles, is the epitome of elegance in a cream shift dress and vertiginous nude heels. Her long, glossy hair is loose; her make-up’s understated and the famous pillow-pout breaks into a smile that radiates warmth.

The cause of her mirth is Black, the rotund, impish actor and musician who came to prominence in the hit comedy School Of Rock.

Dressed in jeans and a black slogan T-shirt, he’s demonstrating “inward breathing” by singing The Beatles’ Blackbird at the top of his voice.

They both crack up and it’s clear why their partnership translated into box office gold in 2008’s Kung Fu Panda, which earned $633 million worldwide.

The tale of a lazy, daydreaming panda called Po (Black) who learns the art of kung fu alongside his idols the Furious Five (including Jolie’s Tigress), the film also earned an Oscar nod for Best Animated Feature Film. Three years on, Black, Jolie and the rest of the cast, including Dustin Hoffman as Master Shifu, have lent their voices once again for the much anticipated sequel, Kung Fu Panda 2, this time in 3D.

“It was like putting on a nice comfortable pair of shoes,” oozes 41-year-old Black.

“Yeah, it was more fun the second time around having all got to know each other,” nods Jolie, 35. “Our characters already had history, so it was fun to jump in and immediately start to play.”

As well as witnessing Po tackle a formidable villain peacock voiced by Gary Oldman, the audience can expect the answer to one of life’s great mysteries: Why is Po’s dad a goose?

Even the most casual of observers must have noted Mr Ping, a noodle-making goose (James Hong), can’t be Po’s biological father.

“Po’s getting flashbacks of his childhood and comes to realise he’s actually adopted,” explains Black, who’s dad to two sons, Sammy 4, and Thomas, 3, with wife Tanya Haden. It was like a funny joke in the first one, the elephant in the room. Obviously he was adopted but there was no talk of it, so in addition to this being a hero’s journey to save the day, it’s also a journey of self-discovery.”

For Jolie, who has three adopted children; Maddox, 9, Pax, 7, and Zahara, 6, as well as three biological children with partner Brad Pitt, Shiloh, 5, and two-year-old twins Knox and Vivienne, the film’s subject matter had particular resonance.

“I wondered if they’d ask me questions about it, but because adoption, birth mothers and orphanage are happy words [in our house,] they’re very used to these discussions. They just felt proud that they were a little more like Po, so it was lovely.”

The kids were actually used as a sounding board for the film.

“As they’re aged from two to 9, we figured it was a good group to gauge whether the film was working and we brought them in,” says Jolie. “I did it for them in so many ways and was excited for them to see it.”

Like the first film, the sequel is hugely influenced by Hong Kong action movies and Po’s newest adventures reflect a deeper immersion into the world of kung fu.

Black says the franchise offered him the opportunity to gain a deeper appreciation of martial arts.

“I did some training in kung fu for both films. It wasn’t just for research purposes; it was also to kind of get in shape.” He pauses for dramatic effect. “What really drew me is the combination of exercise and self-defence, along with the third, sort of unseen, component, a spiritual one.”

Jolie reveals her sons attend martial arts classes too.

“Boys are boys and naturally have a certain kind of energy. It’s been wonderful to get them focused on martial arts and teach them about discipline, respect and how to control their own bodies,” she says.

As with the first movie, it’s Po who remains the emotional crux of the story.

“For a male character, he’s sensitive, so it seems a very nice balance that Tigress is the harder one who learns to be more emotional. Can I say that?” Jolie laughs, looking over to Black who’s feigning shock.

From Lara Croft in Tomb Raider to Evelyn Salt in Salt, Jolie’s synonymous with playing powerful women in action films but off screen, she describes herself as “a mom who’s changing diapers and colouring all night long, so I’m sure I’m very, very soft”.

“I’ve always been drawn to strong characters and I admire strong women emotionally and physically – people who I feel are fighting for something,” she says. “I’ve been very lucky that I came to my career at a time when women are being allowed [to play] these roles.”

Whether Tigress, Po and the rest of the crew return again is ultimately for the audience to decide, says Black: “As long as people love it and hunger for more Kung Fu Panda, there will be more”, he grins.