Robin Thicke knew 'Blurred Lines' was going to be a hit because his grandfather liked it.

The song was one of 2013's biggest tracks worldwide, and the singer knew it would be a smash when his elderly relative told him how good it was.

He told US TV show Entertainment Tonight: ''My grandpa called me when he first heard the song, and he called it before it became a hit, before radio even started playing it, he said, 'You got a hit on your hands there, sonny boy!

''And that's when I knew - my 80-year-old grandpa is telling me I have a hit? Wait a second.''

Robin added he, T.I., and Pharrell Williams recorded the track - famed for his racy video featuring topless models - also got an instant reaction when they played it back for the first time in the studio.

He added: ''We made the record in an hour-and-a-half, and then people started coming in to the studio from the other studios ... All of a sudden we had 20, 30 people just dancing to 'Blurred Lines' in the studio.

''We had that feeling at that time that it was an eight to eighty song for all ages, all colours, all groups, and it's nice that it's become that.''

While a big hit, the track has caused some controversy, after the estate of late singer Marvin Gaye filed court documents in October claiming the song was too similar to the soul star's 1977 track 'Got to Give it Up'. The case is yet to be resolved.