The host was halfway through reading out the audience questions when a lad in the crowd interrupted him.
"Excuse me," he said, "I'd like to ask a question."
You could see he was nervous and a little geeky, and you could also see he had decided he was going to be heard whatever it cost him.
"You're the reason I got into comic writing and I've got my portfolio with me. I've been trying to get in touch with you for a very long time, so would you mind looking at it and giving me some feedback? We could do it backstage after this."
Frank Miller answered without a pause.
"I'll tell you what, we'll do it right here as soon as this interview is over and I'll look at your portfolio."
The room sighed with relief.
Frank Miller is one of the biggest names in comic book writing, graphic novels and film direction too.
He wrote and drew The Dark Knight Returns, a complete revamp of the Batman genre that turned the hero into a dark character with an extremely serious mission and very little fun in his life.
Since this masterpiece, every filmmaker since has followed that version of Batman while borrowing heavily from his storytelling rather than inventing their own.
He went on to write 300 and Sin City, and he was responsible for the modern depiction of Daredevil. Last night he was on stage in Royal Geographic Socieity promoting a memoir of his life - and I was in the audience because my good friend Todd Wade called on Wednesday to say he had something for me.
I nearly said no.
I've been away on Scout camp all week, driving up and down to the New Forest to manage the nights on camp while going back to work in London during the day. I was too tired to be much use to anybody.
Then Todd said the name: "Frank Miller is speaking."
I went quiet as this was too good to miss.
At school I'd studied Miller as my art project of choice, copying all pictures in the Dark Knight Returns and learning to draw the human figure through his interpretation of people.
I loved the way he showed how characters thought and spoke to each othe. He built a fight out of tension and dialogue before anyone threw a punch. I knew the work inside out but I'd never heard the man speak.
He talked more about life than just his work. He talked about taking risks - and about how they do go wrong, and how when they go wrong it is never really as bad as you had braced for.
He mentioned his entire mission to draw and tell stories was pinned on a massive risk that he worked so hard to achieve under a mentor, kind enough to tell him his drawings were not good enough - until one day he said:
"That's not terrible."
He talked about failure too and about the moment where you stop trying to repair a page at the edges and just tear the whole thing up and start again.
When the interview ended, he did exactly what he had said he would do. The kid got his five minutes.
What does it take to give someone five minutes of your time and an honest opinion? Very little, and yet a lot of people at that level would have taken the backstage offer and quietly let it evaporate.
The kid had the courage to ask in a room full of strangers and Frank had the grace to answer him in front of the same room.
It was a lovely thing to see - and it had nothing to do with Batman.
Frank Miller's new book is Push the Wall: My Life, Writing, Drawing and the Art of Storytelling.
