Charlie Hunnam's girlfriend has shared the secret to their happy relationship.

Jewellery designer Morgana McNelis and the 'Sons of Anarchy' actor have been together since 2007 and Morgana says allowing each other to ''grow and evolve'' is hugely important to maintaining a lasting relationship.

She told ''I think the key to maintaining a good balance is creating a safe space within the relationship for both partners in which to grow and evolve. It's very important to be present and participate in each other's experiences so that falling in love doesn't happen just once, it continues to happen over and over.''

Charlie previously admitted he was ''heartbroken'' to pull out of '50 Shades of Grey'.

The 35-year-old actor was cast as Christian Grey in the big screen adaptation of the erotic thriller but quit the role before filming began because of scheduling conflicts, and admitted the decision to walk away from the project was ''emotionally destructive''.

He said: ''It was the worst professional experience of my life. It was the most emotionally destructive and difficult thing that I've ever had to deal with professionally. It was heartbreaking.

''I really, really pride myself on being a professional and a man of keeping my word. It means a lot to me, truly.''