Anyone who's seen a lot of Branagh's filmography is bound to recognize a few of the players from his other films; in fact, Branagh wrote most of the parts specifically for his friends. This is especially fun to play when you consider the cast members who went on to be in Branagh's Hamlet the following year:
Richard Briers plays Claudius here and then Polonius in Hamlet; Nicholas Farrell plays Laertes here and then Horatio; and Michael Maloney plays Hamlet here, and then Laertes.
Apart from that, Farrell and Maloney were in Alan Parker's adaptation of Othello with Branagh as well, playing Montano and Roderigo, respectively.
Of course, Farrell is probably best known to a younger audience as Prime Minister Brian Green. And Briers to that same crowd would be the old man from "A Day in the Death".
Jennifer Saunders steals a couple of scenes near the end as a Southern U.S. movie producer.