Edith Ngaio Marsh was born on 23 April 1895 in Merivale, Christchurch, to Rose Elizabeth Seager and her husband, Henry Edmund Marsh, a clerk in the Bank of New Zealand in Christchurch. His daughter said of him, 'I can imagine nobody less naturally suited to his employment.'
When Ngaio was around seven years old, her parents moved to Valley Road, Cashmere. The house that her father built there was to be her home for the rest of her life. She was educated first at a dame school run by Sibella E. Ross, and then in 1910 was enrolled at St Margaret's College, a private Anglican girls' school with a decided Anglo-Catholic bias. She remained there until 1913, active in literary and dramatic pursuits. Her play The moon princess was performed that year, with her mother taking the part of the witch. The Christchurch Press described it as 'a clever little play'.
Between 1913 and 1919 Marsh attended Canterbury College School of Art as a part-time student, supplementing her income with private tutoring. Here she met Evelyn Polson (later Page), who became a lifelong friend, and Olivia Spencer Bower. She shared a studio in Cashel Street with a group of fellow students who were interested in innovative artistic styles and approaches. The orientation of the college was more formal and academic, but one of her teachers, Richard Wallwork, and his wife, Elizabeth, were sources of encouragement. She also formed friendships with the Acland family of Mount Peel sheep station and the Rhodes family of Meadowbank sheep station. These associations lasted throughout her life, and were of great importance to her. (The Rhodes appear as the Lampreys in A surfeit of Lampreys (1941).)
During this time Marsh was writing articles, poems and stories which were published in the Christchurch Sun. She also wrote a play, The medallion, which she later felt 'must have been very bad in a slightly promising way'. She showed it to Allan Wilkie, who, with his wife, Frediswyde Hunter-Watts, headed the Allan Wilkie Shakespeare Company. Wilkie invited Marsh to join the company as an actor during their 1919–20 tour of New Zealand. Their repertoire was not solely Shakespearean, and Marsh appeared in a variety of roles to mixed notices. When the tour ended she took part in a short tour with the Rosemary Rees Comedy Company, and on her return to Christchurch joined the Wauchop School of Drama and Dancing as a tutor. Her play, Little housebound, was performed by Wauchop in 1924.
Marsh still saw herself as a painter, and in 1927 she was part of an exhibition by The Group, organised to differ from the conservative hanging policy of the Canterbury College School of Art. Although she continued to paint throughout her life, Marsh gradually gave up serious aspirations. She wrote, 'somehow I failed to get on terms with myself'.
In 1928 Marsh travelled to England. Her journey was recorded under her pseudonym, ‘A New Canterbury Pilgrim’, in a series of articles which appeared in the Christchurch Press and were syndicated to other newspapers. On her arrival she stayed with the Rhodes family in Buckinghamshire and in London. With Nellie Rhodes she established an interior decorating shop called Touch and Go, in Knightsbridge. She returned to New Zealand in 1932 when her mother became ill. Rose Marsh died that year.
Before Ngaio Marsh left Britain she had completed the draft of a detective novel, A man lay dead, which she gave to Agatha Christie's literary agent, Edmund Cork of the Hughes Massie agency. He placed it with the publisher Geoffrey Bles, and it came out in 1934. Between 1934 and 1982 Marsh wrote 32 detective stories, shifting to the publisher William Collins in 1938, with American publication by Little, Brown from 1940. At a time when the detective genre was in the ascendant, Marsh became an acknowledged star, one of the constellation that included Agatha Christie, Margery Allingham and Dorothy Sayers.
Marsh works within the classic detective story form, enlivening it with the high quality of her writing and a range of erudite references. While many of her novels have an English village or country house setting and subscribe to a conservative view of society, she is capable of innovation, especially in terms of realistic characterisation and psychology. Several works use theatre as a narrative context. Four have New Zealand settings – Vintage murder (1937), Colour scheme (1943), Died in the wool (1944) and Photo-finish (1980) – and there are many New Zealand references and characters. Her detective, Roderick Alleyn, who appears in all her fiction, displays the standard aristocratic confidence and a rational scepticism about human nature, but is notable, in the age of Peter Wimsey and Hercule Poirot, for his lack of eccentricity. Her father's education at Dulwich College, alma mater of the Elizabethan actor Edward Alleyn, was an influence in the choice of name. Alleyn's friend (later wife) Agatha Troy first appears in Artists in crime (1938). Troy is a painter, and there is perhaps a certain amount of autobiography in the construction of her character.
Between 1932 and 1948 Marsh's life was conditioned by her responsibilities to her father, although she managed a trip to England in 1937–38. Edward Marsh died in 1948. For the remainder of her life Ngaio Marsh divided her time between lengthy visits to England, and her house in Cashmere, where she did her writing. Her appearance, speech and mannerisms have become part of New Zealand folk memory, much imitated and easily recognised (as in, for example, Mervyn Thompson’s autobiographical play Passing through). She was very tall, with a deep voice, ‘cultured’ accent and patrician manner. Her success as a writer and the financial rewards it brought enabled her to indulge in a taste for expensive designer clothes, often of a strikingly dramatic style.
In 1941 the Canterbury University College Drama Society asked Marsh to direct Outward bound, by Sutton Vane, marking the beginning of what was later described as 'a small but unmistakable Golden Age', which ended with the destruction of the Little Theatre by fire in 1948. The emphasis of her work was Shakespearean. In 1943 she directed Hamlet, which, with the production of Othello, toured to Dunedin, Auckland and Wellington in 1944 and 1945. In September 1948 her production of Pirandello's Six characters in search of an author was done in private performance in honour of a visit by the Old Vic Theatre Company. This, and Othello, toured Australia in 1949, and Six characters had a season in London in 1950. In 1951 Marsh was involved in founding the British Commonwealth Theatre Company, which toured New Zealand that year with three of her productions. She continued to work with the Canterbury University College Drama Society (from 1958 the University of Canterbury Drama Society) in other venues after the destruction of the Little Theatre. In 1967 the Ngaio Marsh Theatre was opened and Marsh directed the inaugural production of Twelfth night. In 1972 she directed Henry V, the first production in the James Hay Theatre, Christchurch.
Her directing style was imaginative, meticulous and autocratic, based on her admiration for the theatrical style of London and Stratford. Despite the amateur status of her actors, the results were highly acclaimed. But she was less sympathetic to any sense of an emergent nationalist culture, and particularly disliked the New Zealand accent, which she discouraged. Mervyn Thompson, a playwright, described her style thus: 'Everything in large sweeps. Spectacular visual patterns. Emphasis on swift movement forward of narrative. Rousing climaxes! Large emphasis on tonal variations. Character secondary to "musical" elements. Good "popular" Shakespeare. Great "orchestration". Nothing "dry" left in. Not much in the way of politics either.'
Marsh's autobiography, Black beech and honeydew, was published in 1966 and revised in 1981. She was made an OBE in 1948, and a DBE in 1966. In 1962 she was awarded an honorary degree in literature from the University of Canterbury. Ngaio Marsh never married, and died on 18 February 1982 at her home in Valley Road.