Gary Barlow gets personal with one of the most successful song writers of all time. Max Martin has made hits for Britney Spears, The Backstreet Boys, Westlife, Kelly Clarkson, Pink, Taylor Swift, Ariana Grande, Katy Perry, Celine Dion and more. He's won ASCAP's Best Songwriter of the Year eleven times and sold more than 140 million records. He's also written the West End music '& Juliet' based on his own songs. Successful as he is, Max Martin keeps an incredibly low profile. In this rare interview, he explains how he works, what it takes to make a hit and how he collaborates with the world’s biggest stars.