The Press Association reports that the film will be directed by Downfall director Oliver Hirschbiegel, with the filmmakers saying the biopic will show "how finding true personal happiness for the first time allowed her to achieve her defining successes: evolving into a major international campaigner and humanitarian".

Watts said of the film: "It is such an honour to be able to play this iconic role - Princess Diana was loved across the world and I look forward to rising to the challenge of playing her on screen."

Hirschbiegel added: "I am delighted to have such a truly exceptional actress who embodies the warmth, humanity and empathy of such a global icon as Princess Diana."

Shooting will begin later this year.