Johanna was in the front row during a fight scene of Player Kings at the Noël Coward Theatre when the Olivier Award winner took a fall.
She said he tripped on a bit of prop, and that “he built up momentum and flew head first into me in the audience”.
Johanna said she had her legs crossed and Sir Ian’s head hit her knee “quite hard”.
The 85-year-old says he is having “physiotherapy, light exercise and a lot of essential rest at home” following the fall.