The heartbreak behind YouTube's most viewed song

The co-writer of “See You Again”, which has surpassed Gangnam Style as the most viewed song on YouTube, has spoken of his personal heartbreak behind the lyrics.

Justin Franks told BBC Radio 5 live’s Phil Williams that he cried when he wrote the song, dedicated to a close friend who died and late Fast and Furious franchise actor Paul Walker.

The ballad, sung by Charlie Puth featuring Wiz Khalifa, has been streamed almost three billion times.