Cellier was born in Hendon, Middlesex on 12 July 1928,[1] into a family of actors including his father Frank, his mother Phyllis Shannaw, and his half-sister Antoinette.

Other roles include Pinchard in Georges Feydeau's An Absolute Turkey, Tommy Devon in Aunt Edwina, The Dean of Archeo in Body and Soul, Eric Shelding in The Case in Question, Danforth in The Crucible, Duke Francis in The Dark Horse, Dr. Finache in Jacques Charon's National Theatre production of Feydeau's A Flea in her Ear, Charles Blutham in Juno and the Paycock, Dr. Herdal in The Master Builder, Sir John Tremaine in Me And My Girl, The Chaplain in Mother Courage, Christopher in A Private Matter, Captain Brazen in The Recruiting Officer (replacing Laurence Olivier), Polonius in Rosencrantz and Guildenstern Are Dead Higgins in Ross, Miguel Estete in The Royal Hunt of the Sun and Desmond in The Winslow Boy.

[4] On television, Cellier has appeared in a wide range of programmes since 1955, including detective series such as Softly, Softly and Bergerac, adventure series such as Doctor Who, historical dramas such as The Six Wives of Henry VIII, Upstairs, Downstairs and The Duchess of Duke Street.

[4] He played Roy Difford in the Casualty episode "The Silence of Friends",[5] and the judge in BBC Four's Canoe Man (2010), which recounted the John Darwin disappearance case.

(1973), as the Attorney General; Man About the House (1974), as Morris Pluthero; Man Friday (1975), as Carey; Barry Lyndon (1975), as Sir Richard; Sister Dora (1977), as Actor; Jabberwocky (1977), as First merchant; Crossed Swords (1977), as Mean Man; Holocaust 2000 (1977), as Sheckley; The Pumaman (1980), as Martin; Breaking Glass (1980), as Garage Customer; Chariots of Fire (1981), as the head waiter at The Savoy; And the Ship Sails On (1983), as Sir Reginald J. Dongby; The Last Days of Pompeii (1984), as Calenus; A Room with a View (1985), as Sir Harry Otway, a landlord; Clockwise (1986), as Headmaster; Out of Order (1987), as Home Secretary; Personal Services (1987), as Mr. Marples; Howards End (1992), as Colonel Fussell; Bhaji on the Beach (1993), as Ambrose Waddington; The Remains of the Day (1993), as Sir Leonard Bax; Stanley's Dragon (1994), as Mr. Johnson; Mrs Dalloway (1997), as Lord Lezham; and Ladies in Lavender (2004), as BBC Announcer.