Hip-hop superstar JAY-Z was shocked to discover his friend Eminem wears a bulletproof vest - insisting he feels sorry for the rapper because there is a "dark cloud" hanging over him.

Jay-Z teamed up with Eminem in the studio in 2003, a year after the Stan hitmaker released his highly-acclaimed record The Eminem Show.

The Big Pimpin' star admits he felt body armour under his pal's clothes when he gave him a hug - and he realised the extent of Eminem's problems.

He tells Interview magazine, "I never even told him this, but I remember that Eminem came into the studio when we made Moment of Clarity, which he produced, on The Black Album. So here's Eminem. It's 2003, he was, like, the biggest rapper in the world - he sold, like, 20 million records worldwide or some ridiculous number.

"But when he came to the studio, I remember I hugged him and I could feel that he had on a bulletproof vest. I couldn't imagine being that successful. I mean, he's a guy who loves rap and wanted to be successful his whole career. Then he finally gets it, and there's this dark cloud over him. He has to be afraid to walk around New York freely. I was like, 'Here it is. You’ve gotten everything you wanted, and now you’re a prisoner of your own fame.' That’s sad to me - that you have to walk around in a bulletproof vest after you’ve sold 20 million records. I found it sad."