After Williams quit the chart-topping British boyband in 1995, he publicly attacked Barlow for the way he was treated when he was a member of the group.
But, as Williams solo career went stratospheric, Barlow decided not to retaliate - despite his initial instinct - because his popularity was nothing compared to that enjoyed by Williams.
He says, "When he started the war of words at first I wanted to retaliate. But I never called. My deal was I have had the same mobile number for 15 years - if he wanted to get in touch he could have done.
"His career has got so big I'd never want to be him. Especially when he's at Knebworth. I could never do that, I could never compete so I just kept my mouth shut."