Robert George Deans was born in Christchurch, New Zealand, on 19 February 1884, one of nine children of Catherine Edith Park and her husband, John Deans. His paternal grandfather, John Deans, was one of the Deans brothers who settled in the Canterbury area in 1843; his father owned properties at Riccarton, Homebush and Waimārama. His mother's father, Robert Park, had been chief surveyor for Wellington province.
Robert attended Christchurch Boys' High School from 1897 to 1901. In his last year he was head boy, senior monitor, captain of the First XV and captain of the cadets. After leaving school he worked on the family's Riccarton property and played rugby for the school's old boys' club. In 1903 he first represented Canterbury at rugby. In 1904 and 1905 he played for the South Island, and in the latter year was selected as one of the three-quarters for the New Zealand team to tour Great Britain.
Deans stood six feet tall and weighed 13 stone 4 pounds: a splendid figure of colonial youth. He could run, handle, sidestep and swerve. He was a popular figure among his team-mates, and noted for his generosity towards them; they in turn respected his abstinence from tobacco and alcohol, and his deeply held religious views.
The team – known as the All Blacks – swept triumphant through the British Isles, defeating Scotland, Ireland, and England. Those who had prophesied that ill-disciplined colonials would lose more games than they would win had now to eat their words. Deans had an outstanding tour and scored 16 tries, but his most famous try was disallowed.
In December 1905, before a crowd of 47,000 singing Welshmen, the All Blacks played Wales at Cardiff. By all accounts the Welsh had the better of a fierce game and led 3–0 until the last moments. Then Billy Wallace, picking up the ball on his own side of halfway, 'made a brilliant dodgy run': 'I threw Bob Deans out a long pass which he took perfectly and raced ahead'. As the cover-defence threatened to cut him off at the corner, Deans cut back towards the posts – which would also make the conversion easier – and wrestled his way across the line. The referee, wearing collar and tie and street shoes, was still 30 yards away. The Welsh were there in force and hauled the flying three-quarter back. When the referee arrived he decided not to award the try.
Deans telegraphed his version of the event to the Daily Mail in London, and wrote about it in his occasional column in the Christchurch Press. The English papers endorsed his account; so did a touch judge and several Welsh players. Nobody denied, however, that the Welsh would have been unlucky to lose that day.
Interest in the tour in New Zealand had been intense. Premier Richard Seddon went out of his way to identify himself with its success, and arranged, at public expense, for the team to spend time in America and Canada on the way home. There Deans scored a further four tries.
Deans returned to farming at Homebush after the tour, and continued to play for Canterbury and the All Blacks; he captained Canterbury in 1908. On 30 September 1908 at the age of 24 he died of appendicitis at Homebush. He is commemorated by the Robert Deans Scholarship, awarded annually by his old school to the best all-round boy.