Downton Abbey star Laura Carmichael has revealed George Clooney will be seen planting a kiss on Dame Maggie Smith during his guest appearance with the cast.

Oscar-winner George has a role in a specially filmed Downton sketch to be screened for ITV charity appeal Text Santa later this year.

Laura – who plays Lady Edith – said the cast were unsure whether he would actually take part until he arrived on set.

“It’s amazing and we didn’t even know if it would actually happen until he turned up,” she told ITV’s This Morning.

“We were filming away and then heard ‘he’s here, he’s here, he’s arrived’… But he was wonderful and so brilliant and I’m very excited for everyone to see it.”

When news of George’s role emerged last week, Downton Abbey bosses kept a lid on details including the names of stars from the drama with whom he would share a scene.

But Laura has now told how he will be seen with the Dowager Countess (Dame Maggie), who swoons during their encounter.

She said: “There is a very brilliant moment with Maggie and George – and I don’t know if I want to give away any more than that really – but Maggie does a very comedy fall – George plants a kiss and Maggie ends up on the floor, it’s wonderful. He was hilarious.”