The London-born star, who portrays Sherlock Holmes in hit U.S. TV drama Elementary, has been working in America for several years and wanted to make his citizenship official because of his six-year-old son.

He says, "It was an incredible experience. It's something that had been bubbling away and you work towards it and I really wanted to become an (American citizen). My son is an American citizen, my son was born in the States, so it was important to me to feel a part of my community and I went to a little ceremony and it was really very special...

"It means so much to people here, and that's the really wonderful thing. It's a slightly different dynamic to back home because everyone is so pleased for you and very inclusive and that's the nature of this country, I feel. It's welcoming."

Miller was previously married to Angelina Jolie from 1996 to 1999.