"There are 20 other people standing over you, it is hot and sweaty, you are in clothes that aren't your own and you are doing your very best to look as charming and debonair as possible," the 43-year-old says. "You just hope the director gets a good shot."
"It is good to be doing it with Ada because I've known her for almost 20 years and she is an absolute professional," he continued.
Despite their long spanning friendship Ada told New Idea that filming loves scenes are still pretty awkward.
"They’re not romantic. They’re always a bit awkward, especially in the beginning until you find your groove with the other actor and you talk through things. You just need to make sure that the other person is comfortable, but the more you get to know someone the easier it becomes.
Opening up to New Idea about her on-screen romance, Ada says she was shocked at first to learn about her pairing with James’ character.
"It was surprising at first, because the characters haven’t had that much to do with each other," she said.
"They’ve both been involved in quite different storylines – but then, it sort of makes sense. Leah and Justin are a similar age and they’re the ones who always seem to look after everyone else. But I think they’ve also both got to a stage in their lives where they need a friend to chat to and are ready to have a bit of fun.’
Off-screen, the beloved actor is engaged to his co-star Sarah Roberts. The star announced their engagement in December of last year, admitting that he wanted to get the tick of approval from his six-year-old daughter Scout before he went public with the news.
"My daughter was asking, 'Daddy, who's your friend?'" he told The Daily Telegraph at the time. "So there came a time where once we'd met and sat with Scout, telling the rest of the world was easy."