Luc Besson had to persuade his producers to get Rihanna to star in 'Valerian and the City of a Thousand Planets'.

The iconic 'Fifth Element' filmmaker knew from the start that he wanted to cast the 'Unfaithful' hitmaker in the pivotal role as Bubble in his new sci-fi film, but Besson had to persuade his producers to reach out as they were unsure they could get her in the independent film.

He said: ''Bubble is the ultimate artists - that's the part. And for me, Rihanna is the ultimate - she's the queen. I thought about her from the beginning. And when we started the cast, I said, 'For Bubble, I'd love to contact Rihanna.' They [the producers] said 'What's your second choice?' I said, 'Why?' They said, 'Luc, come on.' I said, 'Why not? Let's try it. Let's see.' The first question we asked to the manager is if she's interested in shooting in the film. If she's not interested, then don't even give her the script. But the guy came back and said, 'Definitely, yes.' ''

Besson - who is married to film producer Virginie Silla - and Rihanna enjoyed a ''normal relationship'' on set he says the R&B singer couldn't have been more ''perfect'' as a professional during the shoot.

He said: ''On set, she was normal. Even me, at the beginning, I said, 'I hope it's not going to be Rihanna and the great orchestra.' But on the first day, she looked at her entourage and said, 'You, out.' No one was on set. She came on set by herself. It was a normal relationship between an actor and an actress. When she got emotional she let me get in. She was perfect. The fact that she is the queen of soul is a handicap, in fact. I don't use that. She's not singing in the film. She's not a superstar in the film. She has a specific role. It's a handicap. And my concern with her was if she wanted to be in the film for the right reason or not, and she did.''

The all-star cast also included supermodel-turned-actress Cara Delevingne, Clive Owen, Ethan Hawke, Rutger Hauer and Dane DeHaan and the cast and director were in London for the UK premiere of 'Valerian and the City of a Thousand Planets' on Monday night (24.07.17).