David Walliams is assisting Robbie Williams in Judges Houses on 'The X Factor'.

David Walliams

David Walliams

The 'Britain's Got Talent' judge admitted he doesn't know the "technicalities" behind what makes a strong performance but thinks he's a good person to help the 'Angels' singer choose his finalists in the Groups category because he knows what sounds good and what is entertaining.

He said: "I'm not a musician, I'm a fan of music but when people start talking about vocal ranges I don't really have a clue. I mean, I can hear when things aren't great, but I don't know the technicalities of it.

"But I think that's OK because I just respond to a feeling, whether I thought people were good or not. The audience know as well, you just know when you're being entertained or not."

And the 47-year-old comic is thrilled to be helping Robbie because he doesn't want his fellow 'BGT' judge Simon Cowell to win with the Girls.

He said: "You know what, the thing about this show is I'm actually a fan of it.

"I've always loved watching 'The X Factor', I've never missed a series. I've actually always wanted to do Judges Houses. I like that I've now done it with Rob because I want him to win, I don't want Simon to win!

"I've known Rob for a long time, so it felt natural that we would do this together. It felt easy, we're not at each other's throats."

David went on to praise Robbie as a judge because he thinks the former Take That singer has the perfect background to mentor aspiring pop stars.

He said: "He's great because he's very empathetic and he's really been there. He's also had his ups and downs as a person and as a performer in terms of his popularity.

"Look back at pictures of him at Glastonbury having left Take That and then you see him as the supreme popstar he is, it's an incredible journey he's been on. Joining Take That at 15, that's insane.

"So when he speaks, he speaks from experience on all fronts.

"I think the contestants trust him because they know he's been there and done it all.

"I think he's had two very different experiences, he's been in a band where to some extent you're told how it's going to be, to then become a solo artist and be able to express himself whatever way he wants, it's interesting, not many people have had both those experiences."