Radcliffe, talking about his new series, A Young Doctor’s Notebook, says, “It’s quite bizarre. It features amputations and syphilis, none of which sounds funny, but it is.” And, on playing Jon Hamm’s younger self in the show, he says, “Facially, we are more alike than you would think, but there it a slight discrepancy in height. But if you can look past that you’ll enjoy yourself.”

Asked about his film, Woman in Black being the most complained about film, he says, “It’s great. I get a strange pleasure from that. It was frightening and I did say not to let your children see it.”

Ennis, describing her celebrity as “Great fun but really surreal,” says, “Seeing big billboards was madness. One night I went to get fish and chips and there was a massive poster of me doing crunches and I couldn’t go in so turned around and went to the supermarket.”

Talking about winning gold at the Olympics, and asked if all the sacrifices have been worth it, she says, “It was an unbelievable and an amazing journey over the past few years. From having an injury in 2008 I could never have imagined getting to this point.”

On meeting Prince Harry at the Olympics she says, “Kate and Wills came past and then Harry said, ‘All right? Not much pressure on you then.’ It was so mad having that experience.” And, on winning the 800 metres, she says, “It was like nothing I have never experienced before. The crowd was so loud and on the final 200 meters they went wild. I have never heard anything like it.”

Asked if she has now achieved everything she wants to, she says, “No, the Olympics were the absolute highlight of my career but I still think I have more to achieve,” adding, “Getting back into winter training has been hard and I was thinking, ‘Why am I doing this?’ but I have to refocus and set different goals. Rio is the long term plan,” adding, “I am sticking to heptathlon for next few years but looking forward to going into one event. Training will be easier.”

Talking about her fiancé Andy and whether there is room in her life for him, she says, “We have been together for a long time and he has been on this journey with me and we’ve experienced it all together. He is always there and comes to as many competitions as possible. He doesn’t want to be in the limelight and is happy to be in the background and support me which is great.”

And, on her ‘Best Celebrity Body’, says, “It is mad. But it is great that it’s a sporting figure that’s out there now. It’s a good image rather than stick skinny women that we see all the time.”

Radcliffe, asked if he's shy about showing his body says, “Apparently not. I do it all the time now. Every film I have done this year I have been naked or at least partially naked.” And, on being ripped, says, “The film I have just done (Horns) was the first time I had to get in shape for something. The director told me to go to the gym and get toned.”

Gervais talking about his own toned physique, says, “I always did do running and kick boxing, but only did it once a year. Now I do it every day.”

Asked to explain pictures of him on Twitter wearing nothing but gold lamé underpants, he says, “It was the day of the Golden Globes and Ellen (DeGeneres) gave them to me and asked me to wear them. I didn’t want to because they were way too small so I took a picture to send her.

“After the awards me and my girlfriend went back to the hotel to celebrate with champagne and then flew off to New York. Now the thing is, when I took off the shorts they ripped so in the bin of the Four Seasons Hotel was a pair of ripped gold lamé hot-pants and a empty bottle of champagne. What did that look like?”

On his new European tour, Gervais jokingly says, “It’s stand up of my greatest hits, some people call it money for old rope.”

Mars joins Norton for a chat about his new album before performing Locked Out of Heaven live in the studio.

And finally, Norton pulls the lever on foolhardy members of the audience brave enough to sit in the red chair.

The seventh episode of The Graham Norton Show will be broadcast on Tuesday, 18 December at 21:00 on BBC Entertainment, channel 120 on DStv.