"I know he will appreciate the experience regardless," the letter read.
"However, I was wondering whether there was any chance Mr Irons would be willing to briefly meet my father at the conclusion of the show?
"He doesn't know I have written this, so there is no pressure if this is not possible. I thought I would at the very least try as he has given so much to our family and to generations of drama students in New Zealand, and asked for nothing in return. A surprise like this would make his trip."
During the meeting the pair talked about the play and their mutual passion for sailing.
Afterwards, Irons told the Post: "We all have that one teacher who inspired us to become the people we are today. From reading his son's letter, it's obvious Gary File is one of those teachers to many of his students.
"I'm so pleased to be able to meet Gary and congratulate him on 40 years of teaching drama to young people. I wish him a very happy retirement and thank him for making the long journey from New Zealand to see us this evening."
Mr File called the experience "surreal" and said he'd admired Irons since the 1980s.
He described the actor as being warm and generous.
"He was so kind and welcoming and interested in what someone like me had to say about the play - when you're talking to one of the world's premier actors it's remarkable.
"It was a bit hard to take in when I was first told I was meeting him after the show and it all happened so quickly.
"I think I'll still be wondering in a week's time whether this really happened or not."
