Williams left the group in 1995, shortly before it was disbanded in 1996, but declined to be part of a reunion more than 10 years later.
Take That reformed as a four-piece and went on to have global success with their next two albums Beautiful World, in 2006, and The Circus, which became the fastest selling album of 2008.
In 2010, it was announced Williams would be rejoining his bandmates Gary Barlow, Jason Orange, Howard Donald and Mark Owen, much to fans' delight.
Williams confesses he was surprised at the fans' positive reactions after such a long hiatus and admits that he was jealous of the band's success without him.
He tells British Tv channel Sky1, "When the boys first got together, I was pretty much, 'Oh, right, Ok... ' Then it was, 'They've sold 275,000 tickets... they've done what?'
"I was gobsmacked. Gobsmacked in all manner of everything. Sort of, 'Wow, we meant that much to people, that's great. They mean that much to people (again)? S**t!
"I think it was confusion more than anything. (I was) pleased for the boys - you know, not too pleased that I wanted them to take over the joint (the music industry). It was like, you know, they can have a certain level (of success). Just don't smash the living daylights out of it, like they did."