Mansfield matriculated from Napier Boys" High School in 1923 and studied art in Dunedin at the King Edward Technical College with William Allen and Robert Nettleton Field. In London Mansfield studied pottery at the Camberwell School of Art & Crafts, bookbinding at the Central School of Art & Crafts, and design at the Reimann School.
After four years teaching at the Feilding Agricultural School (now Feilding High School) he travelled to London in 1934 to continue his studies. Mansfield served with the British army from 1941 to 1946. He was repatriated to New Zealand but returned to London in 1947.
Instead of adopting the traditional decorative motifs of the bookbinder, he looked to contemporary fine art for inspiration.
His bold and expressive designs, derived from the language of abstract art, helped to revitalise the craft of bookbinding during the 1940s and 1950s. He continued binding, though less consistently, until 1976, when failing eyesight forced him to give up the craft and return to sculpture and drawing.
Mansfield returned to New Zealand following his retirement. Though largely living in England for most of his adult life he visited New Zealand frequently and maintained contact with New Zealand friends and artists, thinking of himself as “a New Zealander through and through”.
Between 1981 and 1985 plans were made for a book about Mansfield to be published by Ian and Joyce Vigor Brown, owners of the Vigor Brown Gallery in Napier.
A text was commissioned from anthropologist Terence Barrow, Brian Brake photographed Mansfield"s sculptures, Mansfield wrote a text about his life and approach to his work, and the Governor-General of the time Sir David Beattie contributed an introduction. The book never reached publication but a slightly edited version of Mansfield"s text, with Brake"s photographs, was printed in the journal Art New Zealand in 2007. In the text, on the topic "The Importance of Lincolnshire", Mansfield wrote
Foreign more than sixty years drawing and especially line drawing, has played the vital role in all my work.
So has music, notably the violin — a line "singing".
I love the words of Paul Klee — "taking a line for a walk". lieutenant has been the adventure of these lines, and the resulting shapes and spaces, between and beyond, which has been my primary interest.
Hundreds, possibly thousands of creative drawings, have evolved my personal development in art, and provided the source background of my bookbinding and sculpture, which are essentially tooled drawings on an almost flat surface. First president of the Guild of Contemporary Bookbinders (1955–1968)
Officer of the Most Excellent Order of the British Empire (1979)
Fellow of the Royal British Society of Sculptors (1980)
The Mansfield Medal awarded in the annual British Designer Bookbinders Society competition is named in his honour.