The secret story behind how Catherine Tate created the character 'Nan'

Catherine Tate has revealed the story behind her famously foul-mouthed character Nan, who has been amusing the public since 2004.

Speaking to Three's The Project ahead of her New Zealand tour, Tate said Nan was actually inspired by an experience volunteering at a home for the elderly.

Tate was there to sing to the residents and help them remember the past fondly - but there was one resident that wasn't having any of it.

"I won't say what she did say because it was rude, but you'll have to fill in the lines," Tate said.

"In between my singing she said, 'Is she going to stand in front of that f**king telly all day?'"

The unnamed woman didn't inspire the character's look though - that's all from Tate's imagination - although it doesn't take much to turn her into Nan.

She's been performing as the character for her tour, and initially tried several different prosthetics for the costume.

But they all proved too difficult and with the audience a few metres from the stage Tate has them fooled without any at all.

"I was absolutely mortified when no one noticed that I wasn't wearing prosthetics," she said.

Watch the video for the full The Project interview.