Although not from an acting family (her father was a distinguished London doctor), she was already performing in plays at the age of 5 and even writing them at the age of 8. Sears had a long association with France and French culture which began in her childhood when she spent summers in Brittany with pen friend Michelle. This is when she learnt to speak fluent French. After leaving school she spent time in Paris doing voice overs and dubbing work and enjoying the company of the Paris “in crowd” of artists and writers such as Pablo Picasso, Albert Camus and Arthur Koestler. When she was sixteen she followed her elder sister Ann Sears (1933–1992) to the Central School of Speech and Drama in London. During her last year she signed a 7-year contract with Romulus Films which allowed her an annual six months to do stage and television work if she wished. This was made possible through the good offices of the film director Jack Clayton, her friend and mentor. After graduating from drama school, she was active from 1955 onwards in the Windsor repertory theatre. A year later she made her film début with a minor role in Michael Truman’s Touch and Go (1955) and followed this up with a part in Maurice Elvey’s film version of comedy Dry Rot (1956) as the naive Susan Before she turned 22, Sears had made her début on the London stage, replacing Mary Ure in the part of Alison in John Osborne’s Look Back in Anger, playing alongside Richard Bates and Richard Pasco. Shortly afterwards she played Claire Bloom’s role in the television production of Ring Round the Moon. Although her greatest contribution was in the area of repertory theatre (her preferred medium), her most enduring legacy is inevitably in films, mostly in the late fifties and early sixties, but also in her television work.

It was David Miller’s film The Story of Esther Costello (1957) which led to a breakthrough in her film career (at the age of 21) and international acclaim. In this film based on the novel by Nicholas Monsarrat, Sears appears in the title rôle as a girl of 15 who loses her sight, hearing and power of speech as the result of a traumatic childhood accident (the explosion of an arms cache in her native Ireland). She is adopted and brought up by a rich American society lady (played by Joan Crawford who also actually chose Sears to play the part of Esther). Although the film itself was fairly lacklustre, it was her performance which impressed the critics more than anything else. She had to convey everything through her facial expressions which was an area in which she was to prove particularly gifted and which lent itself to close-ups that can only be achieved on film. It was after this film that she married Tony Masters who had been one of the two art directors of the film. A year later she was nominated for the Golden Globe award and also received the British Film Academy award for best British actress of the year — both for The Story of Esther Costello. After this initial success, she alternated between film and theatre until the mid-1960s. In London she appeared at the Royal Court Theatre with Alan Bates and Richard Pearce in Jean Giraudoux’s The Apollo of Bellac under the direction of John Dexter, in Michael Hastings’ Yes, and appeared at the Lyric Theatre, Hammersmith in Julien Green’s play South. On screen, she was cast as Susan Brown, the naive daughter of an industrial magnate (Donald Wolfit), who falls for social climber Joe Lampton (Laurence Harvey), in Room at the Top (1959). Directed by Jack Clayton, it was adapted from the novel by John Braine. Sears had a lifelong friendship with actress Simone Signoret, who stars as her married rival for Joe Lampton’s affections.

Sears was in Australia to act in the last Ealing film The Siege of Pinchgut (1959, known in the USA as Four Desperate Men) in which she plays the part of a girl hostage (daughter of the caretaker of the tiny island fort of Pinchgut in Sydney Harbour) who forms a romantic liaison with an escaped convict (abetted by his brother and two accomplices) who has taken the caretaker and his family prisoner in an attempt to clear his name. The film ends in a dramatic shoot-out with the authorities. It later became a classic of the Australian cinema. One year later, in the film adaptation of Lawrence’s semi-autobiographical novel Sons and Lovers (1960) directed by Jack Cardiff. She appeared as Miriam, the girlfriend and intellectual companion of Paul Morel (Dean Stockwell). In Hammer’s production of The Phantom of the Opera (1962) she played the opera singer Christine Charles on whom the Phantom (Herbert Lom) has become fixated. Her singing voice was dubbed by opera performer Pat Clark. The Black Torment (US: Estate of Insanity, 1964), in which she played Lady Elizabeth. the second wife of the male lead, was her last feature film for many years.

Sears work commitments reduced to bring up her three sons, Adam, Giles and Dominic. However, Sears continued to do some work for television and appeared in many BBC and ITV dramas until 1981. She also appeared in two more plays: as Grusha in Brecht’s The Caucasian Chalk Circle at the Chichester Festival Theatre in 1969 and also in Alan Ayckbourn’s comedy How the Other Half Loves in London’s West End. In the 1970s she returned to provincial repertory theatre. She was based at the Haymarket Theatre in Leicester where she played title roles in classical plays by Sophocles (Antigone and Elektra), Shakespeare, Goldsmith, Dostoyevsky, Ibsen (Hedda Gabler) and Strindberg (Miss Julie), but also in the work of more modern playwrights such as Liane Aukin (Little Lamb) alongside Bill Wallis and Perry Cree, Brecht (The Caucasian Chalk Circle), Ayckbourn (How the Other Half Loves), Rattigan and Pinter. She also toured with the One-Woman-Show playing Virginia Woolf. She later appeared in a television film adaptation of Dickens’ semi-autobiographical novel Great Expectations (1974) as Biddy. In 1989 she made her last screen appearance in The Last Day of School directed by Amin Q. Chaudhri, in which she plays a working mother who supports her husband, and makes a mark for herself as an entrepreneur. In the last ten years of her life she travelled extensively, spending many months in Mexico, China, Italy, North Africa and Egypt. Her husband, Tony Masters, died in May 1990 whilst on holiday with her in the south of France. They used to go there every year during the Cannes Film Festival. She did not remarry. Heather Sears died in early 1994 of multiple organ failure, at the comparatively early age of 58, at the family home in Hinchley Wood near Esher, Surrey. Her son Adam Masters is now a film and television editor, while his brothers, Giles and Dominic, are feature film art directors.