Simon Cowell is surprised after being selected to mentor the Over-25s category on 'The X Factor' this year.

Simon Cowell

Simon Cowell

The 53-year-old star admits he wasn't expecting to be given the group again after leading Ben Haenow to victory last December, but thinks he can still help this year's contestants "do great things."

Shortly after it announced which category each judge will mentor this series, the music mogul, who previously revealed he was hoping to secure the girls, wrote on Twitter: "Wasn't the category I was expecting. I did win last year with the Overs so I'm sure we will do great things this year."

The judges and categories were paired up by fans of the show for the first time ever this year, who voted via the social networking site.

Cheryl Fernandez-Versini will oversee the Groups, while new judges Nick Grimshaw will mentor the Boys and Rita Ora will look after the Girls.

Despite winning in 2014, Simon recently admitted he thought the last series was "irritating" and "predictable."

He explained: "It felt very predictable during the live shows. There were a load of people we knew weren't going to win who we just had to put through week after week. We knew one of them was itching to get out so he could go in the bloody jungle (Jake Quickenden) but that's just one example of why it was irritating.

"We did the room auditions, then you go to Wembley (for the arena stage) and it was like ground hog day. The same thing again but with a bigger crowd."