The pair have been friends for 16 years, since Louis began mentoring Brian's band, Westlife, so who better to dish the dirt than Brian?
"Louis is the biggest gossip on the planet!" Brian, 34, tells us.
"He rings me every two to three weeks and starts the conversation with, 'Wait till I tell you this!' I get all my goss from Louis."
"But I will tell you this, Louis is still the same today as the first day I ever met him. He hasn't changed.
"Actually, he looks even younger now," Brian laughs, perhaps in reference to his 'make-over' two years ago, including a £30,000 hair transplant.
Louis will be the first celebrity guest on Brian's new show, Who's Doing The Dishes?, a cross between Through The Keyhole and Come Dine With Me, where four members of the public are invited to a celebrity's house and have to guess who the star is by identifying clues from the star's cooking.
"He's rubbish," Brian tells us. "And of course I knew that before I asked him onto the show. He's not used to receiving criticism back, he's just used to amusing people and laughing at people."
READ THE FULL INTERVIEW IN THIS WEEK'S REVEAL MAGAZINE!