"But I have no interest in questioning him about it. Never. I don't think I'd get the answers I wanted," said Gaze.
"And I don't know what knowing answers to certain questions would give me now either."
Watkins was sentenced to 39 years in prison in December 2013, following a series of serious sex offences involving children. The 36-year-old admitted to the attempted rape and sexual assault of a child under 13, but pleaded not guilty to rape.
He also confessed to conspiring to rape a child, three counts of sexual assault involving children, seven involving taking, making or possessing indecent images of children and one of possessing an extreme pornographic image involving a sex act on an animal.
"I tried reading the judge's report. I couldn't even finish it," said Lewis. "To think that somebody I grew up with, who I had been friends with my entire life, whose mother I knew, and how close our families were - to even imagine him ... I find it utterly unbelievable that he was capable of doing those things. Obviously he did, but how somebody can...
"I don't understand it, I'm afraid."
Although the band knew that Watkins was struggling with drug addiction, Gaze said that there was "was absolutely nothing that led us to suspect what he'd done".
"He was always surrounded by all these women, so it just seemed impossible," he said.
At first, Watkins denied the allegations to his bandmates.
"[Ian] spent the longest time trying to convince us that somebody was trying to get revenge on him," recalled Gaze.
"He'd created such a web of people, bouncing these women off each other, that it was perfectly feasible that one of these women hated him so much that she wanted to catch him out."
Karen Ruttner - who dated Watkins for years, before becoming a part of the Lostprophets management team after their relationship ended - "cried every day for three months" following his guilty plea.
She has been undergoing therapy to help her deal with what's happened.
"This person that I had been so close with at that point, for six years, was ... capable of this? I thought I knew when he was lying," she said. "I thought I knew what his demons were. This was not on the list of presumed demons."
An inquiry is currently being held into whether the celebrity status of Watkins may have prevented him from being brought to justice sooner.
- Independent