Kempthorne Prosser & Co. Ltd, also known as the New Zealand Drug Company Ltd, was the leading drug and fertiliser manufacturer in New Zealand from 1869 until 1978. The company's full name was Kempthorne Prosser & Co.'s New Zealand Drug Co. Ltd, established in Dunedin. Thomas Whitelock Kempthorne and Evan Prosser entered into business together in 1870 as chemists. They set up Kempthorne Prosser, which became a limited liability company in 1879. The head office was set up on Stafford Street in City Rise, Dunedin. In 1904 Thomas Whitelock Kempthorne retired. Kempthorne Prosser & Co became Kempthorne Prosser & Co. Ltd in 1879 when the New Zealand Drug Company was formed. Superphosphate In early 1881 the NZ Government offered a bonus for three years to any company that would manufacture 50 tons of sulphuric acid per year. KP's NZ Drug Company was the first in the country to combine sulphuric acid and bone dust to produce superphosphate. The Burnside Chemical Works in Dunedin was the first of its type in New Zealand. Kempthorne Prosser constructed further superphosphate plants in Auckland, Christchurch, and Wanganui. From this stemmed a major chemical fertiliser industry, of national importance to the agricultural and pastoral economy. For almost a century 'K. P.' was to dominate the market. Prosser resigned from the company in 1886 and went to Australia before committing suicide. By the mid-1970s, some New Zealand farmers decided it was time to take control of the fertiliser industry, and established a new company, the Ravensdown Fertiliser Co-operative Ltd. With help from Brierley Investments and producer board funds it acquired Kempthorne Prosser in 1978, and Kempthorne Prosser exited the market. In 2014 there were 25,062 shareholders in Ravensdown and it was New Zealand's leading fertiliser company. 'Ravensdown' as a name comes from the 'Raven', taken from the Ravensbourne site combined with the 'down' taken from the Seadown site. Ravensdown was described by the High Court, in March 2021, as causing a 'reputational risk' to New Zealand by importing phosphate rock mined illegally in Western Sahara. The imports have attracted criticism that Ravensdown has found difficult to shake off. Kempthorne Prosser operated four large chemical works. The Burnside, Dunedin Works (1881), Westfield, Auckland (1887), Hornby, Christchurch in 1922 and the Aramoho, Wanganui (Wanganui Chemical) Works in 1926. Chemical works and buildings In 1870 the firm erected its first premises, on Stafford Street, City Rise, Dunedin. This row