This year marks a hundred years of the greatest rivalry the rugby world has known, New Zealand against South Africa. These titans first met on a test field in 1921 and, coincidentally, in the hundredth year of their battle for supremacy, they will also play their 100th test. The intense, unmatched rivalry carries a storyline like no other: it's not just about the physical struggle on the hard grounds of South Africa or in the depths of a New Zealand winter, it's also about the clash of two cultures and how attitudes shaped the sporting history. New Zealanders and South Africans first met on makeshift football fields during the Boer War and there was immediate acknowledgement of a mutual respect for rugby prowess. This continued during the First World War and culminated in an army team touring South Africa, a tour that itself led to the first official tour of New Zealand in 1921. For their first two series, in 1921 and 1928, they could not be separated. Then South Africa gained dominance in 1937 and 1949, but New Zealand regained the ascendency in a memorable 1956 series that enveloped the whole country. And, so it's continued, often against a backdrop of the starkly different attitudes the two countries had to racial equality. The professional era provided a different playing field and different circumstances, but the rivalry has been no less intense, the competition no less demanding.