Mirren plays Queen Elizabeth Ii in the new West End play and she acts alongside real-life corgis, the monarch's pet of choice, in the production.
However, Daldry admits they faced a dilemma in the run-up to opening night this month (Mar13) when the animal, appropriately named Lizzy, appeared to suffer a bout of stage fright.
He tells Britain's Sunday Telegraph newspaper, "She was excited the first three times, and then I think she decided she didn't want to be an actress any more. She decided to retire from the British stage. Now she's back home, a resting actress, resting by the fire."
Lizzy was replaced by another corgi, but Des Jordan, of the Animal Actors agency which provided the dogs, insists the creatures are being very well treated and even have their own dressing room at London's Gielgud Theatre.
He adds, "I look after them better than my own children. I have to. They are doing an important job and no one would be happy if anything happened to them."