Smithyman was born in Te Kōpuru, a milling and logging town on the Wairoa River near Dargaville, in the Northland Region in the far north of New Zealand.
[1][2][3] Some of Smithyman's poems, especially in Imperial Vistas Family Fictions (written in 1983-1984 and posthumously published in 2002) are about his father and other relatives from previous generations whom Smithyman had never met, including his grandfather, also named William Kendrick, born in 1829, who became a sailor, fought for the British Royal Navy in the Crimean War, travelled to Australia and India, then became harbourmaster at Ramsgate on the southeast coast of England.
[1] In August 1946, at Auckland, Smithyman married the poet Mary Isobel Stanley (née Neal; 1919–1980), whose first husband had been killed in the war.
In lectures and articles he promoted special needs education for psychologically impaired and high-achieving children, and the training of special-education teachers.
The English poets T. S. Eliot, W. H. Auden, Dylan Thomas and Americans John Crowe Ransom, Allen Tate, Robert Lowell and Marianne Moore were all influences.
At this time Smithyman wrote ironic, anti-Romantic love poetry thick with syntactical complexity, dense argument, and many references.
According to Ian Richards, the poem "Flying to Palmerston", which Smithyman wrote in an airport lounge in 1966 and which later became the title piece for the 1968 book, "signalled a new start in a new manner" in the poet's verse.
A six-month stay in 1969 at the University of Leeds as a visiting fellow in Commonwealth literature resulted in travel in Britain and North America, which stimulated many poems.
[1] On returning home in 1970, his poetry engaged the landscapes, history and people of his native Northland, as seen in Earthquake Weather, as well as The Seal in the Dolphin Pool (1974), and Dwarf With a Billiard Cue (1978).
[6] Some of these works became his most admired verse and are his most anthologized poems, including "An Ordinary Day Beyond Kaitaia", "Tomarata", and "Reading the Maps: An Academic Exercise".
Concerning New Zealand, he wrote about Coromandel ("Colville" and "Where Waikawau Stream Comes Out"), Auckland ("About Setting a Jar on a Hill"), the coast around Pirongia ("Bird Bay", "Below Karioi"), and other areas in the Central North Island ("In the Sticks", "Tokaanu").
[7] In 1980 Smithyman's wife died after a long illness, and in January 1981 at Auckland he married Margaret Ann Edgcumbe, like himself a university tutor.
[1] Smithyman's other writing in his final years included essays on New Zealand philology and critical editions of novels by William Satchell and the stories of Greville Texidor.