Greg Berlanti was delighted with the "instant" chemistry between 'Fly Me to the Moon' stars Scarlett Johansson and Channing Tatum.

The 52-year-old filmmaker has overseen the romantic comedy drama that takes place during the 1960s Space Race and was thrilled to notice an immediate connection between the leading pair because they didn't have a chemistry read beforehand.

Greg said at a West Hollywood screening of the film: "They both can have chemistry with a wall, but you don't know until you have them together.

"However, I knew from the second the read-through was happening it was instant and I knew I just needed and wanted to keep watching them. They have that thing."

The film – which centres on the relationship between a marketing specialist and a NASA director - is set to be released in cinemas next month but Greg explained that that wasn't planned until test screenings proved successful.

He said: "It was originally direct to streaming.

"But then we handed in the cut and started testing it. We tested it in Denver and it went very well. We tested it in California and we tested it in Texas. Every time, it was very much a resounding response from the focus group and testing that this was a theatrical movie."

Berlanti explained how the audiences at test showings were particularly "grateful" to see an original story play out on the big screen.

The director said: "The other thing that the testing audience also kept bringing up was wanting to see an original movie. They were so grateful for an original.

"Even though it's obviously historical fiction, it's an original story wrapped around that. They didn't know what was going to happen in a way in the movie and that was so fresh for them."