The former All Saints singer's marriage to the Beady Eye frontman was rocked earlier this year by the revelation he fathered a secret love child with US journalist Lisa Ghorbani, and now Robbie - who was engaged to Nicole in 1998 - has defended his former flame, insisting she's a ''very decent person'' and deserves better.
He told The Sun newspaper: ''I have a very big soft spot for Nic because she's a very decent person.
''I feel sorry for her as she deserves to be in a good place, in a happy marriage, and I thought she was with Liam. But it would appear that they weren't.
''Nicole really doesn't deserve all that from Liam. I've very, very fond memories of her. She's a sweetie.''
The 39-year-old singer is now happily married to Ayda Field and has a 13-month-old daughter, Theodora Rose, with the actress and he believes he has found someone he can feel content with in a monogamous relationship.
Robbie said: ''I think you're very lucky to find somebody you can coexist with without straying or going mad or being angry. That's whether you're Liam Gallagher and Nicole Appleton, Robbie Williams and Ayda Field or Tim and June from down the road. Luckily I'm in a relationship where we are heading in the same direction -- but Liam and Nicole weren't.''
Take a look back at October's inaugural event.
The film is expected to continue without Mendes' involvement.