Conversation so far:
What did Harry Houdini's mirror challenge consist of?
The London Daily Mirror newspaper challenged Harry Houdini to escape from special handcuffs.
Was Harry Houdini able to escape the Daily Mirror's special handcuffs?
After an hour and ten minutes, Harry Houdini emerged free.

Question: Who all was there?
Self-contained rewrite: Who all was there to see Harry Houdini's escape from the Daily Mirror's special handcuffs?