Complex sentence: In 1976 Hordern joined the RSC in Stratford-upon-Avon, where he appeared as Prospero for Trevor Nunn in "The Tempest", an engagement which the actor found to be unpleasant because of his poor relationship with the show's director, Clifford Williams.
Split into simpler sentences: In 1976 Hordern joined the RSC in Stratford-upon-Avon, then directed by Trevor Nunn. Hordern played Prospero in "The Tempest," an engagement which he found unpleasant because of his poor relationship with the show's director, Clifford Williams.