Usher's teen parties with P. Diddy

P. Diddy used to take Usher to wild parties when he was only 14.

The 'OMG' hitmaker was mentored by the hip-hop mogul when he signed to Bad Boy records as a teenager and P. Diddy - who was then calling himself Puff Daddy - would let him go along to his extravagant bashes to give him more of an "edge".

Usher - who now mentors Justin Bieber - explained: "Puffy's idea was to make me a bit rougher with more edge.

"But I'm not saying Puff was wrong. That first album wasn't my most successful but it launched the career I've enjoyed for 18 years since. It's helped me understand the importance of having a mentor when I'm working with Justin. You have to make music relevant for now."

Michael Jackson was also a hugely important figure in Usher's development as an artist, and he admits singing Larry Grossman and Buzz Kohan's 'Gone Too Soon' at the King of Pop's memorial service after his untimely death in June 2009 was one of the most conflicted experiences of his life.

He said: "That was the hardest yet most gratifying moment of my career. The song summed up what people were feeling as nobody believed Michael had passed. He was such an iconic figure, icons like him live forever.

"Michael was very serious about his craft. He'd say don't get caught up in whatever that moment is, be mindful that you're always making history. It inspired me."