The 57-year-old star, who plays High Court judge Fiona Maye in the forthcoming adaptation of Ian MCEwan's 2014 novel, and the film's director Richard Eyre dropped in on proceedings in London.

During a break in the case being heard at the court, Emma was even allowed to take the place of the presiding judge on the bench.

According to British newspaper The Times, while in the judge's position she commented, "I feel so powerful up here."

When a woman who was at the centre of the ongoing case returned to the courtroom, she was reportedly shocked to see Emma apparently taking control of proceedings but said, "I'm a great fan of yours."

The Children Act follows legal high flyer Fiona as her private life begins to fall apart while judging a high profile case involving a family of Jehovah's Witnesses who refuse a blood transfusion for their 17-year-old son on religious grounds.

The novel and film's title comes from Britain's 1989 Children's Act, legislation which allows authorities to intervene when parents refuse to cooperate with officials to ensure the welfare of their offspring.

No further casting announcements for the movie, which is yet to receive an official release date, have been made.