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8 January 2015 Last updated at 05:47 GMT
In his latest film Testament Of Youth, it's short and straight. So Kit turned to a wig.
"It was one of those things I was quite concerned about, We knew we couldn't cut my hair because it was close to the filming of Thrones so we wigged it.
"It was done really well by a really good guy and it didn't distract because it can be one of those things that really takes away from a performance if there's a wig that looks wrong."
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There's always lots of talk about Kit Harington's long curly hair, which he's contractually obliged to have to play Jon Snow in Game of Thrones.