The star joked to Us Magazine that pressure to land the role of student revolutionary Marius began soon after he mailed in an audition tape of himself singing 'Empty Chairs and Empty Tables'.
"That was the start of what become like an American Idol, X Factor-style audition," he teased. "It was so intense - I have new respect for people of those shows."
Redmayne added humorously: "The only thing missing was Paula Abdul and Simon Cowell!"
He went on to credit co-star Amanda Seyfried with brightening up the Les Misérables set once he finally won the role of Marius.
"She's like this amazing ball of light and that's exactly what the part needs. Les Mis is fairly dark at moments, and when she comes on screen, everything just lights up," Redmayne beamed.
"It was nice being with her in London, getting to hang out with her."
Redmayne was recently cast in the Wachowskis' upcoming sci-fi movie Jupiter Ascending opposite Mila Kunis and Channing Tatum.
Les Misérables is showing in US cinemas now, and opens in the UK on January 11, 2013. Watch a trailer below: