The 41-year-old actor and comedian welcomed daughter Mabel, his first child, with fiancee Laura Gallacher last November (16). And while he had contemplated starting a family previously, it wasn't until he saw his little girl that he realised he was meant to be a father.

"It's about the way that switches on something in you as a man," Russell said of parenthood as he was interviewed on U.K. TV show This Morning on Friday (03Feb17).

"When I first saw my daughter I felt like some latent part of myself got switched on in that moment, something to do with my own femininity and fathomless love that I had previously speculated upon but not accessed."

Being father to Mabel has also made the multi-talented star question his previously understood concepts of gender - both consciously and subconsciously.

"Now that I have these very important women in my life I have re-evaluated the way that I unconsciously looked at gender, because now I've got a daughter I think 'wow, I don't necessarily need to dress her in clothes that are indicative of her gender'," he explained. "Why would you? Just see how she formulates. I've become quite sensitive to that and aware of it."

While he is relishing being a first-time father, Russell finds the new level of responsibility he has for his child extremely daunting. But welcoming Mabel into the world has made the Forgetting Sarah Marshall star completely change his life to adapt to fatherhood.

"I think you have to evolve because it's quite an abrupt and sudden change, one minute you don't have a baby and then suddenly there is a new relative who lives in your house, not a moderate or minor relative like an uncle, a full-on person who is dependent on you," he laughed.

Many celebrities have chosen old-fashion names for their offspring in recent years, with Emily Blunt opting for Hazel and Violet and Zooey Deschanel choosing the moniker Elsie for her daughter. Asked how he and Laura chose the name Mabel for their baby girl, Russell explained they waited until she was born before they settled on a name.

"I wanted to stare at her to make sure it was the perfect name for her," he admitted. "You have got to name their essence, you look at them, 'What is their essence?' I feel like she had a twinkling sparkling joyousness to her."