Boris Johnson admitted he had written a rap on the Queen's silver jubilee.

The London Mayor – who met Will Smith at a celebration for Mr Johnson's Leadership Clubs, which offer extracurricular activities for 10 to 14-year-olds – told the actor: "My first rap, I haven't really set it to music yet. Perhaps with your help. I can send you a lyric. It was about the Queen's silver jubilee."

Smith joked: "That was big in the hip-hop community."

The pair also share Aristotle's Poetics as an inspiration and Mr Johnson said: "Aristotle's book could be called the Pursuit Of Happiness," referencing Smith's Hollywood hit.

Smith replied: "It's very big for film. You see, we've got a lot in common."

Smith and his son Jaden were surprise guests for the 90 children taking part in the workshops.

The father and son arrived to the trailer of their new film, After Earth, with Jaden performing a spontaneous rap for the children.

He spoke about working with his father and said: "He has, as you can see, all the experience you ever need. So, if you ever need anything on set, you can just walk over and ask him. He's like a walking dictionary.

"Any time I'm lost or anything, I can just ask him."

The 14-year-old actor and rapper named Shakespeare and Kanye West among his greatest influences and said he would never tell his father if he became more successful than him.

He said: "Even if I did it, I would never say it."