Mark Ronson has admitted that it took half a year for 'Uptown Funk' to be completed.

The producer and musician unleashed the track in December and it has become a global smash hit.

Speaking to The Sun, the Brit revealed that Bruno Mars - who features on the track - was difficult to pin down when making the tune.

This meant that the song took a number of months to finish as a result of his schedule.

Ronson said: "Bruno was on tour a lot, so we'd work on the track when we had one day free in LA. Or if he was in London playing Wireless we'd be in my studio.

"It took around six months to finish with all the to-ing and fro-ing. I had to chase him around to finish that song."

The single meanwhile is currently at No.1 in both the UK and the US.

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Watch the video for 'Uptown Funk' below: