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Ready for a chat: Jennifer Lawrence, Chris Pratt and Jamie Oliver appeared on BBC One’s Graham Norton Show in London on Friday night

At which the surprised 26-year-old actress cut in saying: ‘Oh God, how do you know about this?’

And she raised her glass to whoever it was that spilled the beans, as the audience laughed.

It turns out that Jennifer was wearing a wet suit for a scene when her bum became itchy, so she sat on a rock and began rubbing it back and forth to scratch it.

‘It ended up coming loose,’ Jennifer giggled. ‘And it was a giant boulder and it rolled down this mountain and it almost killed our sound guy!’

‘Oh God, how do you know about this?’ The 26-year-old actress was caught off guard when Graham asked her about one incident during filming on The  Hunger Games in Hawaii and jokingly raised her glass to whoever had spilled the beans

To make matters worse the rocks are sacred to the indigenous people  ‘and you’re not supposed to sit on them,’ she added.

‘It was this huge dramatic deal and all the Hawaiians were like, “It’s the curse!” And I’m over in the corner going, “I’m your curse. I wedged it loose with my ass.” ’

Jennifer looked chic in a black velvet dress and jacket with her blonde hair in an elegant updo for the interview.

And here’s the story: Jennifer was wearing a wet suit for a scene when her bum became itchy, so she rubbed it against a rock that came loose,  ‘rolled down this mountain and almost killed our sound guy,’ she admitted

Promo tour: Graham with Jennifer, Chris and celebrity chef Jamie Oliver. The two actors were on the show to talk up their new sci-fi flick, Arrivals

She and Chris Pratt were on the show to promote their new sci-fi movie, Passengers.

They play two people who wake up 90 years too soon from an induced hibernation on board a spaceship bound for a new planet.

Also starring Michael Sheen, Andy Garcia and Laurence Fishburne, it’s due out on December 21 in the US and the UK.

Early risers: Jennifer and Chris play two people who wake up 90 years too soon from induced hibernation on a spaceship bound for a new planet in Passengers, due out December 21