Jack Denham was born at Campsie in Sydney in 1924 and began a riding apprenticeship under his father Joseph, a Canterbury-based trainer, in 1938. When Joseph Denham died in 1939, his papers were transferred to his brother Mick. He gave away riding in 1943 to work in his brother's stable and in 1948 was granted a training licence after Mick was disqualified over a positive swab. Denham trained his first winner at Newcastle in August, 1949, a New Zealand bred gelding by the name of Eloquent and became the dominant provincial trainer in NSW in the 1950s with his stable jockey Doug Weir.

He won his first Group One race with Persian Link (Doomben Cup) in 1955 and was the leading trainer at Canterbury before he joined forces with the late Stan Fox to establish the Nebo Lodge stable at Rosehill. Denham's training career took off when he became a trainer at Nebo Lodge, a position he held for 10 years, training over 1000 winners. For six successive years, from 1971 to 1976, he was runner-up in the Sydney trainers’ premiership table to the greatTommy Smith. He was to win the premiership later in 1990/91 and 1992/93. Denham trained the winners of more than 4000 races over a career spanning 60 years, including 59 Group One races with his numerous stars.

From 1980 onwards Denham was closely associated with owners Geoff and Beryl White, for whom he won a Golden Slipper with Marscay, an Epsom Handicap, Yalumba Stakes and other group races with Filante, and an Australian Guineas and AJC Oaks with Triscay. His greatest triumphs came in 1997 and 1998 when the Denham trained Might and Power took out the Melbourne Cup, Caulfield Cup and Cox Plate. A winner of 15 races from 32 starts, Might and Power rose to national prominence with those victories in the 1997 Caulfield Cup and Melbourne Cup. He went on to win the 1998 Cox Plate, ridden in all three races by Jim Cassidy.

The Zabeel gelding also recorded a number of Group 1 wins in Sydney including another big double in the Autumn of 1998; a five-length victory in the Tancred Stakes at Rosehill Gardens and three weeks later a 10-length win in the Queen Elizabeth Stakes at Royal Randwick.

Throughout his career, Might and Power won races at each of Sydney’s four Australian Turf Club courses.

On 14 December 2009, Jack Denham died at the age of 85 after a long illness. His son, Allan Denham carried on in his father's footsteps. Denham junior never had huge numbers when training at Rosehill - but he always had a top-class galloper. The best of them was champion Eremein, winner of five Group 1 races including the AJC Australian Derby, The BMW and Queen Elizabeth Stakes, plus more than $4.6 million prizemoney; brilliant sprinter Spark Of Life, 2000 Melbourne Cup runner-up Yippyio and AJC Australian Oaks winner Heavenly Glow.

A member of a Sydney training dynasty, Denham first rode as a jockey for his brother, and then trained a champion