Mark Hamill pays tribute to Carrie Fisher, Daisy Ridley and John Boyega talk about the secrecy surrounding Star Wars, Gwendoline Christie talks about some of her more extreme fans and Sam Smith performs live in the studio.

Mark Hamill, asked about meeting the royal princes at the premiere, says, "I jumped at the opportunity to ask them to settle an argument I had with Carrie. Years ago, when they revealed that Leia and Luke were brother and sister, I asked her, 'Does that make me royalty?' Her answer was a most emphatic, 'No!' It turned into a running gag between us so I asked the princes, 'Can you settle this for me. If my mother was Queen Amidala, my father was Lord Vader, and my sister was Princess Leia, doesn't that make me royal?' William said, 'Absolutely it does' but Harry said, 'I'll have to look into that some more.' It was frustrating because I wanted a unanimous decision!"

Talking about his cameo role in the closing minutes of 2015?s The Force Awakens, Mark says, "I trained for a year for that part! I never missed a session at the gym. It was probably wise that J.J. (Abrams) didn't tell me the role was so small because I don't think I would have been motivated to get in shape and I could have been the size of Marlon Brando under the robes."

And, on whether he had to be persuaded to return to Star Wars after such a long break, he says, "I wanted to get away from being Luke Skywalker and the fame that surrounded it so did a lot of good character parts on and off Broadway. I appreciate it now in a way I couldn't in my 20s. When George (Lucas) invited Carrie and me to lunch my wife said, 'I bet they are doing another film,' and I just laughed. When he did offer us the film, Carrie said, 'I'm in' within seconds but I kept my poker face and it took me weeks to decide. I was interested but terrified at the same time because it's so big."

Asked about the secrecy that surrounds the film these days, Mark says, "No one cared when we first did it. We passed the script around to anyone that was interested. But, by the second film the scrutiny had become crazy. Only three people including me were told that Darth Vader was Luke's father and I kept that secret for a year and half. When it finally came out Harrison was very cross and said, 'Hey kid, you didn't f**king tell me that!'"

Talking about Carrie's inability to keep a secret, he adds, "You couldn't tell her anything. Harrison and I would test her - if you wanted to get things out there fast you would tell Carrie it was a secret and she would tell everyone!"

Asked more about Carrie, he says, "It hit us all so hard. I am not sure I have gone through all the grieving yet. You want to grieve in private but everyone wants to talk about her because she belonged to the world. She was just so wonderful." Gwendoline adds, "The film has become a love letter to her."

John Boyega, talking about the possibility of appearing in the final instalment of the trilogy, inadvertently nods but says, "I can't say. I'm not allowed," Adding, "In the last scene of the last film I was slashed and when I saw blood I thought, 'Wow, that mortgage is not being paid now!' I'm so glad to be back."

Asked if he found it hard keeping the storylines secret, he says, "I just can't keep anything a secret so I have to tell just one person - my roommate Stephan knows everything."

Daisy Ridley, talking about keeping the secret that she had been cast in the second film, says, "I was at the theatre and suddenly got a text from George asking me to call him. My heart was pounding and in the interval I called him. I got myself all worked up as I thought I had to convince him but he just said, 'You are in the next film.' I had to go back into the audience and sit through the play. It was such a long play! I couldn't say anything to anyone. It was nuts."

Asked if her family are fans of Star Wars, says, "Not so much. My dad may or may not be the person that asked Mark who he played in the film!" John interjects, "My whole family came out in force at Kensington Palace and the only thing my dad said was, 'Where is the proper food?'"

Gwendoline Christie reveals that appearing in the film was a dream come true, "I have been a Star Wars fan since I was six years old so being in it was hugely overwhelming. I loved Princes Leia but it was more about Carrie - I loved her spirit, her energy and her wit. She was so intelligent and vivacious, which made me think - as someone outside the traditional norms of what was considered attractive - that there was hope for me as an actor and being yourself in the world. She was a huge inspiration."

Talking about some of her more obsessive fans, she says, "I was once followed into a bathroom and as I sat down in the stall a hand with a phone came under the door and a disembodied voice said, 'Selfie' I was horrified and replied, 'No thank you!' I'm really not sure what they wanted in terms of image!"

Mark, with a little help from Graham's special effects department and an orange from the fruit bowl, demonstrates his Jedi telekinesis super powers.

Sam Smith performs Too Good at Goodbyes live in the studio before joining Graham for a chat.

Asked why his second album is a little less than cheery, he says, "I'm not that guy and I've been really unlucky in love but I enjoy writing love songs." Raising an eyebrow, he intriguingly adds, "I'm excited that the third one will be happy and joyous!"

Talking about winning an Oscar, he says, "I can't look at it. It's hidden in my house. I'm waiting until I am 60 or 70 and then I will surround myself with my albums and my Oscar and cry and eat!"