Jon M. Chu knew immediately that Cynthia Erivo and Arianda Grande were his perfect Elphaba and Glinda in the Wicked movies.

The director insisted he wasn't put under any pressure by the studio when it came to casting decision and both Cynthia, 38, and Ariana, 32, immediately won him over, both individually and with their joint chemistry.

He told the Variety Awards Circuit Podcast: "At first I thought, let's keep it open to anybody. The studio never put pressure on us about names or followers. Not one word.

"When Cynthia walks in and sings, you feel it in your bones. And when Ari sat there and became Glinda, there was no question.

"I knew what everyone is seeing now - I got to see it on day four."

Jon worked closely with cinematographer Alice Brooks, editor Myron Kerstein and composers John Powell and Stephen Schwartz on the movies and said working with his own handpicked team was a dream come true.

He explained: "All of us are underdogs. Nobody in the business fully believes in us, and we're used to that. You've always got to prove yourself on the next movie. That mentality doesn't get us down - it fires us up.

It's about being able to feel uncomfortable in those unknown moments and know that you're protected on all sides. If you don't know the person, everyone's trying to protect their own reputation. But this - we live in the uncomfortable. We search for that thing."

And, the experience of making the Wicked movies is something that will stay with him forever.

He said: "When you live with something for five-plus years, and you dream about it and wake up with nightmares right in front of you, it sticks with you. I have not processed it yet."