Charlie Hunnam has spoken openly and in-detail for the first time about the reasons that led to him dropping out of the Fifty Shades of Grey movie. The Sons of Anarchy was the first choice to play billionaire Christian Grey but left the project weeks before production and was replaced by Jamie Dornan.

Charlie Hunnam Sons of AnarchyCharlie Hunnam struggled to juggle his Sons of Anarchy role with other projects

Now, the Sons of Anarchy star is ready to discuss the situation, blaming an overloaded schedule for causing a "nervous breakdown".

"I wouldn't have signed up in the first place if I didn't want to do it," he told Moviefone.

"I was going to finish 'Sons' at like 11 p.m. Friday night, get on the plane Saturday morning to Vancouver for 'Fifty,' missing the whole first week of rehearsal and start shooting Monday morning," he added, "And I was going to shoot that film, wrap that on the Wednesday and the following Monday I was going to start shooting (director Guillermo Del Toro's) 'Crimson Peak' in Toronto."

"I just had like ... frankly, something of a nervous breakdown."

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Hunnam's exit left producers scrambling around for a replacement, with Irish model-turned-actor Dornan landing the role. However, the Sons of Anarchy actor was not put off by the erotic nature of the movie - as was speculated at the time - and was actually drawn to the project after becoming convinced by director Sam Taylor-Johnson's take on the character.

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"Because 'Fifty's going to be massive, it's going to be huge. I really didn't want to fail on such a grand scale and I just couldn't transition from ('Sons of Anarchy' character) Jax Teller to Christian Grey in 48 hours," Hunnam said, "I bit off more than I could chew and it was painful. I loved the character and I wanted to do it."

The Fifty Shades of Grey movie, starring Jamie Dornan as Christina Grey and Dakota Johnson as Anastasia Steele, hits cinemas on Valentine's Day 2015.