Aubrey Mallalieu died before the release of the film .
H.H. Asquith, the Prime Minister whose name occurs (as Herbert Asquith) at various points throughout "The Winslow Boy", was in fact the father of that same Anthony Asquith who directed this film.
The film's screenplay adds the trial scenes, which all take place offstage in the play. The role that Francis L. Sullivan plays was added for the film.
The original Broadway production of "The Winslow Boy" by Terence Rattigan opened at the Empire Theater on October 29, 1947 and ran for 214 performances.