Tonights theme: Number one Singles.

Dermot O'Leary hosts the first of the live shows. Thousands of singers auditioned across the UK and their numbers have been whittled down so that now only the 12 finalists remain to battle it out for a life-changing record contract. Each finalist is mentored by one of the judges - Dannii Minogue returns from maternity leave to support the boys, Cheryl Cole looks after the girls, Simon Cowell is mentoring the groups and Louis Walsh is helping the contestants in the new over-28s category. Tomorrow night, the first act will leave the competition.