Simon Cowell lost for words after X Factor contestant's caustic claim

X Factor judge Simon Cowell found himself at a loss for words, when one of the hopefuls called him "caustic."

The 55-year-old TV mogul was shocked after yoga teacher Mary O'Sullivan performed Celine Dion's Ave Maria for her audition, and asked to sing another song.

"I like you because you're quite ballsy," said Cowell, to which O'Sullivan replied: "But you're caustic."

There were more familiar faces in store for the X Factor judges, as tonight's episode opens with some returning names.

Rita Ora, who was a guest judge on the ITV singing competition in 2012, recognised 21-year-old Havva Rebke, who made it through to Boot Camp that year.

She is hoping to get further in the new series, as she offers her take on Jessie J's Masterpiece.

Renetta Eagle and Ebony Cantwell were formerly part of REAformed, which was Alesha Dixon's Golden Buzzer act on the 2014 series of Britain's Got Talent. The pair are hoping for another crack at fame as they perform Amerie's track Gotta Work with Naomi Mulumbala, Tonia Gigli and Amy Nash as PYT (Pretty Young Things).

Brodie Kelly, who stacks shelves at a supermarket in Bedfordshire, auditioned for The X Factor last year but did not make it past the first round. He hopes to impress the judging panel, which also includes Cheryl Fernandez-Versini and Nick Grimshaw, with his take of Plain White T's Hey Delilah.

There were flirtatious sparks between Ora and Kelly, as well as 23-year-old teacher Joe Waller.

Trio Sunday Club - Lewis Cambridge, Jake Birnie and Seb Kinder, who are all 24 - also caught Ora's eye, after host Olly Murs dubbed them "the hottest boyband we've ever seen".

"Guess what? I'm 24 too," exclaimed the newly-single Poison singer.

The X Factor airs at 8pm on ITV tonight.