The son of a British army captain, Hordern debuted on the London stage as Lodovico in "Othello" (1937). After serving in the Royal Navy during World War II, he returned to the stage as Torvald Helmer in Ibsen's "A Doll's House" (1946). Hordern acted in nearly twenty Shakespeare productions and won acclaim for his interpretation of Chekhov, first in the title role of "Ivanov" (1950) and later as Gayev in "The Cherry Orchard" (1973). He also explored the works of contemporary playwrights like John Mortimer ("The Dock Brief", "What Shall We Tell Caroline" 1958) and Edward Albee ("A Delicate Balance" 1969) and was a close friend and fishing partner of Stoppard (for whom he also appeared in "Enter a Free Man" 1968).

Hordern's active film career began in 1939 when he starred in Carol Reed's "The Girl in the News". He turned in a memorably "chain-rattling" performance as Jacob Marley, whose agonized screams in "A Christmas Carol" (1951) rightfully disconcerted star Alastair Sim. After playing Cicero in "Cleopatra" (1963), he continued his association with Elizabeth Taylor and Richard Burton by portraying Taylor's father in Franco Zeffirelli's "The Taming of the Shrew" (1967). His lecherous Senex in "A Funny Thing Happened on the Way to the Forum" (1966) marked the first of five collaborations with director Richard Lester (which included "How I Won the War" 1967; "The Bed Sitting Room" 1969; "Juggernaut" 1974; and "Royal Flash" 1975). He was the well-meaning Parson Adams in Tony Richardson's "Joseph Andrews" (1977) and also appeared in "Trio" (1950), adapted from stories by Somerset Maugham, Anthony Mann's "El Cid" (1961) and Richard Attenborough's "Gandhi" (1982), among his many credits.

It was on television that Hordern became most recognizable to American audiences. He debuted on US TV in "The Scarecrow of Romney Marsh" ("Walt Disney's Wonderful World of Color", NBC, 1964), and he attracted considerable attention for his work on PBS's "Masterpiece Theatre", starring as Willie Ashden in "Cakes and Ale" (1976) and Reverend Simeon Simcox in "Paradise Postponed" (1986) in addition to acting in four other productions, including his final performance in "Middlemarch" (1994).

Late in his career, his voice was in as much demand as his visage, and he provided narration for a host of film and TV projects, beginning with Stanley Kubrick's "Barry Lyndon" (1975). He served as narrator for "Watership Down" (1978) and was the voice of "Paddington Bear"(1981) in the popular syndicated children's TV series. In keeping with the times, he even appeared in a music video with Barry Gibb of the Bee Gees in 1984.