Linda Bassett, recently confirmed for Churchill's Love and Information at the Royal Court, will also take up a role, as will Nicholas le Prevost in the role of Ralph Lumsden (Uncle Vanya, Dandy Dick), Selina Cadell (The Habit of Art and Peter Egan (Noises Off, The Crucible).
Frances de la Tour has won three Olivier awards, and has worked extensively with Bennett plays before, having taken on roles in his The History Boys and The Habit of Art. Other credits include farce Boeing Boeing, Antony and Cleopatra with the RSC and Eugene O'Neill's A Moon for the Misbegotten. She also took up the role of Madame Olympe Maxime for the Harry Potter films.
People, announced in January, remains shrouded in secrecy - the only details available are that the play has a contemporary setting, the name of le Prevost's character, and the fact that Bennett wrote it.
Bennett and Hytner, whose recent collaborations include The History Boys and The Habit of Art, have reportedly been working together on the play's script over the past year, and had de la Tour in mind for the lead part throughout the process.
The Daily Mail's Baz Bamigboye said: "Hytner and I have had a handful of conversations about People over the past several months, but he has steadfastly refused to reveal the nature of the piece; not even a strapline."