In 1924 the herd became the only one in the State tested for tuberculosis. This forward thinking confirmed Camden Park was at the forefront of the dairying industry. In 1926 a Special Milk, more suitable for children and invalids was inaugurated by Arthur Macarthur-Onslow and his son Denzil. The result was Camden Vale Milk, “the milk with the golden cap”.
After the death of Elizabeth Macarthur-Onslow in 1911 Camden Park House was occupied by her daughter, Miss Sibella Macarthur-Onslow CBE, and then by her eldest son Major-General the Hon. James William Macarthur-Onslow. Upon his death in 1946 the House passed to his eldest daughter, Lady (Helen) Stanham. Camden Park House then passed to Lady Stanham’s son Richard Quentin Macarthur-Stanham. The current residents are her grandson John Macarthur-Stanham and his family.
During World War II work on the Estate was carried out by the Land Army girls working in the fields, orchards and dairies.
In 1950, Camden Park confirmed it was no mere relic of a grand historical past, but the farm of the future. The Rotolactor was the ultimate in modern milking machinery
In the early 1970s control of Camden Park Estate, which until this point of time had been wholly owned by descendants of John Macarthur, passed into third party hands. Some years later and after the closure of some of the activities conducted on the Estate, including the orchard, the NSW State Government acquired a significant portion of the land that Camden Park Estate owned.