SCROLL DOWN FOR VIDEO
Rather than wait for Simon to arrive, David took matters into his own hands, telling fellow judges Amanda Holden and Alesha Dixon: "I think we really need someone to fill that seat. Actually my mother is here today, she's going to be Simon Cowell if she doesn't mind. Come on mum!"
Kathleen filled in for Simon, who was running late
Kathleen proved she was more than up to the challenge as she used her buzzer on several acts, giving Simon a run for his money with her straight talking critiques of the performances. She told one act, 'The Blue Bag Lady': "I thought it was nice music ruined by stupid movements… I’m afraid it’s a no from me", and asked another performer: "You didn’t look very happy when you were singing that song. Were you annoyed about something?".
The other judges couldn't help but laugh over Kathleen's no nonsense comments, with Amanda saying: "It is weird how much you are like Simon, you’re very similar.". She also praised Kathleen's ability to say no to performances, saying: "David is quite a wuss about pressing his buzzer... He just doesn’t seem to be able to give any criticism that’s bad, he’s sweet really. But Kathleen, she pressed hers first once, I was like, 'Woah!'".
David said it was "surreal" to see his mum on the panel
David chatted off camera about how surreal it was to see his mum on the panel. He said: "Once a year Simon is always very late to the recording so we have to start without him. This year it coincided with my mother being in the audience.
"It was quite surreal, it was like having a really odd dream about the show. When you have dreams things are not in their rightful place, so I was like, 'What is my mum doing sitting in Simon Cowell’s chair on Britain’s Got Talent?'".
Kathleen was finally won over by a pair of gymnasts and gave her first yes, saying: "that was absolutely fantastic. It’s a yes from me, definitely" while Ant and Dec cheered at her decision from backstage.
Britain's Got Talent airs Saturday, 8pm on ITV.