Margot Robbie is the best actor director James Gunn has ever worked with.Earlier this year, it was announced that the 53-year-old filmmaker would write and direct DC Comics' upcoming movie The Suicide Squad, which is the highly-anticipated follow-up to the 2016 movie.

Filming began last month on the flick, with original stars including Margot, Jai Courtney and Viola Davis returning to the sequel, alongside newcomers John Cena, Idris Elba, and Taika Waititi.

Despite only working with the Australian actress for a few weeks on the set of the film, Gunn believes she is the best in Hollywood.

"She might be the best actor I've ever worked with," he told a fan during a Q&A session on his Instagram Stories, before adding that he also worked on the Oscar-nominated star's Harley Quinn spin-off movie, Birds of Prey.

The filmmaker also opened up about Doctor Who star Peter Capaldi, who was cast in The Suicide Squad in an unknown role.

"He's blowing my mind with how good he is," Gunn shared, before adding that he was a big fan of the Scottish actor in the 2009 political comedy In The Loop.

Elsewhere in the Q&A, Gunn was asked if he was "limited" with his ideas while making the Guardians of the Galaxy movies in the Marvel Cinematic Universe.

"Kevin Feige asked me to include Thanos and create an origin for the Infinity Stones in Volume One," he said of his experience with the Marvel boss on his first film, Guardians of the Galaxy.

"Other than that I've never been asked to include any story point of connectivity in either Guardians, and I've been given completely free reign by DC."