Curiously, Andrews will voice a key role in Aquaman, the franchise hopeful from DC Films and Warner Bros. and starring Jason Momoa.

The Sound of Music star will voice Karathen, a mythical sea creature that helps Momoa's waterbound hero broker peace between Atlantis and the dry land, an individual familiar with the project told Variety.

Aquaman opens on December 21 in the US, two days before the release of Mary Poppins Returns, when Blunt will take on a role originated by Andrews in the 1964 Disney classic.

The news was first reported by Entertainment Weekly.

"We wanted the Karathen to have the voice of a classic British actress, albeit somewhat digitally altered," Peter Safran, a producer on Aquaman, told the magazine.

"And when we found out Julie was interested and available and excited to do it, casting her was a no-brainer," he said.

Andrews has steadily booked voice work in recent years, in animated blockbuster series like Shrek and Despicable Me.

She has not appeared on screen since the 2010 family comedy Tooth Fairy with Dwayne Johnson.

Australian Associated Press