Speaking on Steve Wright’s Radio 2 show on Friday, the mogul said that he had no idea who would be appearing at auditions on that day – and that Susan’s performance took him and his fellow judges completely by surprise.
“It wasn’t a great day,” he said, “She came on and I thought I don’t think this is going to be great, I’ve just got a feeling here, and she started to sing.
“I didn’t think at the time, to be honest with you, that this was incredible,” Simon admitted.
“I remember thinking this is great but Piers and Amanda got it more than I did and then when I watched the clip back and saw the whole story, that is when I thought this is going to be huge and I’m going to look like a complete idiot.”
The Scottish singer became internationally famous after her original audition was shown on Britain’s Got Talent in 2009.
She went on to finish second in the show to Diversity and since then has enjoyed huge success around the world with her debut album I Dreamed A Dream.