Margot Robbie thinks Peter Capaldi will bring "gravitas" to 'The Suicide Squad'.

The 63-year-old actor will star in the DC Extended Universe sequel as The Thinker and Margot - who reprises the role of Harley Quinn - is convinced the former 'Doctor Who' actor will do "justice" to the part.

Margot told Den of Geek: "The character is definitely done justice.

"He's such an exceptional actor and he's such a lovely guy ... It's funny, it's a huge cast, but we really all did do a lot together. I don't want to give away anything, so I won't tell you what to expect, but he brings gravitas to the role."

Peter joins stars such as Idris Elba, John Cena and Sylvester Stallone in James Gunn's flick and previously explained how he loved the "positive and warm" atmosphere on set.

He said: "I've just got to say what an amazing experience it was, in regards of (director James Gunn) and all of (my co-stars). You know, the atmosphere on that set was so positive and what a warm, wonderful supportive place to be.

"Not everyone has been in a big superhero movie, even if they've been Doctor Who or anything like that. So to walk on to a set like that can be quite intimidating. But the welcome that (everybody) provided was just fantastic."

James previously suggested that fans don't need to watch 'Suicide Squad' before they see 'The Suicide Squad' as the plots are unrelated.

A fan quizzed the filmmaker on Twitter, writing: "I didn't see the 2016 'Suicide Squad'. Will I be hopelessly lost if I didn't watch it before seeing yours?"

James replied: "No, you will be just fine."