Leonard Seton Otway was born on 6 February 1894 in Mount Eden, Auckland, the eldest of three children of Loftus Hastings Otway, a surveyor, and his wife, Mary Russell Puckey. Known as Seton, he grew up on his parents' farm at Elstow, where horses were an integral part of life. He was educated at Elstow School and Auckland Grammar School. While there he represented Auckland province at clay-bird shooting, an activity in which, along with duck shooting, he retained an interest throughout his life.
As a young man Seton Otway was taught horsemanship and the basics of thoroughbred breeding by John Lennard, a Yorkshireman. Unable to afford well-performed mares from top sire lines, Otway selected horses with impeccable breeding on the dam side: half-sisters to top performers but not necessarily great horses themselves. He bought his first mare at the age of 18, and later, with Lennard's advice, he acquired Persis, a mare who was to establish a line of major stakes-winners in New Zealand and Australia. His next acquisition was Lady Marie. These brood-mares, along with their female offspring, proved highly successful when put to Otway's stallion imports. In his judgement the perfect filly had to have the 'head and neck of a fairy, the chest and shoulders of a duchess, the back of an alderman and the arse of a cook'.
On 21 July 1920 Otway married Sydney Alice Clayton in Auckland; they were to have two sons and a daughter. The couple initially leased a property near Elstow, before moving to a 200-acre dairy farm at Kiwitahi. In 1930 Otway bought a 300-acre run-down dairy farm on the banks of the Waikato River, south of Cambridge. There he established Trelawney Stud, the future home of some of New Zealand's top stallions, and for many years the most influential thoroughbred stud in Australasia.
In 1935, with financial support from his father, Otway imported the English sire Foxbridge for £2,625. Twice the British Empire's champion sire, this remarkably consistent horse was New Zealand's most successful stallion and brood-mare sire for 11 consecutive seasons. His female offspring were to produce five Melbourne Cup winners: Hiraji, Foxami, Macdougal, Hi Jinx and Silver Knight. Foxbridge's potency was illustrated at Ellerslie Racecourse on Boxing Day 1944, when his progeny won six races on an eight-race card.
Seton and Sydney Otway were divorced in 1937, and on 19 July that year, in Auckland, he married Helen Ruth White; they were to have one son. In 1950 Otway travelled to Britain and Europe to search for a successor to Foxbridge. He returned with a French stallion, Marco Polo II, and an English stallion, Khorassan, acquired from the Aga Khan. Marco Polo II sired the 1964 Melbourne Cup winner, Polo Prince, and Bali Ha'i, a winner at Ascot; both were descended from Foxbridge mares. Khorassan sired one of Australasia's outstanding stayers, Tulloch, widely regarded as one of the best horses New Zealand has ever produced.
Progeny from another of Otway's British imports, Alcimedes, included two Melbourne Cup winners, Galilee and Silver Knight; the latter was descended on the dam side from Foxbridge and another successful Trelawney sire, Nizami. Otway's ability to select prepotent sires was a reflection of his knowledge and sound judgement. He stated that he was lucky in his choice of stallions, but it was his management of sires and choice of brood-mares that produced top-quality horses in spite of using stock that was not the best available.
Seton Otway's success in breeding Melbourne Cup winners and selecting a string of outstanding sires is unmatched in New Zealand. His horses won races in Australia, New Zealand, the United States, Japan, South Africa, England and Malaysia. Progeny from Trelawney Stud made New Zealand's National Yearling Sales a popular destination for international buyers, and helped make this country one of the world's great thoroughbred nurseries.
A tall, willowy figure, Seton Otway had a keen sense of humour and loved to tell yarns about horses. Many people sought his advice and he was always willing to share his knowledge and give an honest answer. In the 1970s he relinquished the management of Trelawney to his youngest son, James. However, he retained an interest in the stud until his death, at the age of 94, in Cambridge on 29 January 1989; he was survived by his second wife and his children. His ashes were interred alongside those of his 'two old mates', Foxbridge and Alcimedes, at Trelawney Stud.