The 211 remaining X Factor hopefuls have been put through their paces at boot camp – and faced some of their biggest challenges so far.

The first part of the weekend’s X Factor double bill saw the acts being put through their paces at London’s Wembley Arena – performing group songs, solo songs and for the first time having to learn a dance routine.

And once again Simon Cowell and Louis Walsh were joined by Pussycat Doll Nicole Scherzinger – who stood in for Cheryl Cole while she was recovering from malaria.

But it wasn’t all plain sailing for the performers – who had a fight on their hands from the start when Simon told them half of them would be sent home after the first day.

Firstly they all had to sing in their respective groups – with the over 28s performing Lady Gaga‘s Poker Face and the groups tackling Starship’s 80s chart-topper Nothing’s Gonna Stop Us Now.

The boys, meanwhile, had to sing Michael Jackson’s Man In The Mirror while the girls took on Beyonce‘s If I Were A Boy.

The task caused problems for some, including 20-year-old Tobias Sumpton, who was left in tears after giving a poor performance.

“I’ve been practising all day,” he said, “but in front of the big audience and all that I was nervous.”

As a result, Tobias was one of the unlucky ones who found themselves being sent home at the end of the first day, as the finalists were whittled down to the top 100.

Controversial singer Chloe Mafia also made her mark, after claiming she had been out all night the day before boot camp began.

“I haven’t been to sleep yet,” she said, “I’ve got the same make-up on that I had on yesterday morning. I just look disgusting.”

However she performed well enough to make it through to the next day, along with hotly tipped hopefuls Gamu Nhengu and 16-year-old Cher Lloyd.

The second day saw the remaining performers working with choreographer Brian Friedman to perfect a complex dance routine.

But while some of the acts – including girl group Husstle – jumped at the chance to show off their dance skills, others struggled. Irish singer Mary Byrne, who suffers from arthritis in her knees, found the dance difficult while teenager Zain Malik walked off stage at one point and refused to take part.

However, after a pep talk from Simon he changed his mind. “You can’t just bottle it,” the mogul told him, “you are ruining this for yourself.”

The final day saw the acts take to the stage in solo performances, with standouts including Cher Lloyd’s own spin on Coldplay‘s Viva La Vida – featuring a self-penned rap.

“I’m a little bit frightened that they don’t understand what I’m about,” she admitted afterwards. “I’ve just got to do my best.”

Another 16-year-old, Liam Payne – who reached the judges’ houses in 2008 – was also hoping to impress the panel, but ultimately divided them with his performance of Oasis‘ Stop Crying Your Heart Out. “I like him,” Simon admitted, “but I think it was a little bit one-dimensional.”

Teenager Tom Richards also left the panel undecided with his version of Live And Let Die. “I think he looks like he should be in a boy band,” Nicole said.

However they were impressed by the final performance of the day, from painter and decorator Matt Cardle.

“Do you know why we hadn’t noticed him before?” Simon said, following Matt’s performance of The First Time Ever I Saw Your Face. “He’s got no confidence or self-belief at all.”

The second part of boot camp can be seen on Sunday night on ITV1 at 7.45pm.