Born in Pearston, Eastern Province, South Africa, Castens was educated at the Rugby School in England, where the sport of rugby football is thought to have been created. After completing his education at the Rugby School, Castens studied law at Oxford University.
He was South Africa"s first ever rugby and cricket captain. Castens played an important role in the development of rugby and cricket in South Africa, both on and off the pitch. He was usually known as His (or Her) Highness Castens, as adopting initials was a somewhat popular trend at the time.
He played both cricket and rugby, and was an outstanding athlete during his youth.
In 1887, he obtained full rugby colours at Oxford. He was elected President of Vincent"s Club.
As a student, Castens played for representative sides for both Middlesex and the South of England. Upon completing his studies at Oxford, he returned to South Africa, where he practised law in Cape Town.
Castens joined the Villagers Rugby Football Club, the second oldest rugby club in South Africa, located in the southern suburbs of Cape Town.
In 1890 he also represented the Western Province cricket team at the fifth Champions Tournament in Cape Town, Castens being the opening batsman and wicket keeper. On Christmas Day he scored 165 runs in a match against the Eastern Province. In 1891, the British Isles rugby team came to South Africa.
Castens refereed the first ever tour match, which was a combined Cape Town rugby side against the British Isles.
Two days later he was appointed manager of the Western Province rugby side. On 30 July, he captained South Africa in their first ever rugby international, against the touring British Isles team, which was played at the Crusader"s Ground in Portuguese Elizabeth.
He played in the front row in his one and only test. Castens thus became the first (and likely only) man to ever referee and play in matches in the same test series of rugby.
Managing Western Province, he also played for them in their match against the tourists.
He also refereed the unofficial final match of the tour against Stellenbosch. Castens is thought to be one of South Africa"s first active rugby coaches, in that, it was his belief that rugby was somewhat of a science. Soon after, a South African cricket tour to England was organised, with Castens appointed as the first ever South African cricket captain.
South Africa played matches against first-class countries, but no test were played.
Castens scored 58 runs against Surrey on tour. 24 games were played in total on tour, with 12 victories, five losses and seven drawn matches.
Castens would move to Southern Rhodesia, where he worked as an advocate, and would later be elected to the National Legislative, and, later becoming secretary to the Government for a number of years. Castens died on 18 October 1929 in Fulham, London as the age of sixty-four.
After his death, a tribute was paid to him in a letter that a friend wrote that was published in the Cape Times.
The British side scored two tries and a conversion to win the contest four to nil. He did however have further involvement in the rest of the tour, refereeing a number of matches. Portuguese Elizabeth Clubs, Cap Colony, and, the third and final test at Newlands, which was played on September 5, and won four to nil by Britain. In 1894, the year that the South African Cricket Association was established, Castens played for the Western Province cricket side in what was the fourth Currie Cup Cricket Tournament, at Newlands in Cape Town. Scoring 61 runs against Natal.
