Agent in theatre or opera - old B&W movie

I’m looking for the title of an old black and white movie.

The beginning of the movie was about how a group of people (perhaps military officers) talks in a room in England in English. Then they sends someone to Poland ( It is possible that it is a comedy and someone had to pretend to be an agent in the theater or opera). The film is made in United Kingdom probably ( possibly Dutch or French coproduction).

Thank you in advance.

“To be or not to be”?

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