Des Vœux became stipendiary magistrate and superintendent of rivers and creeks in British Guiana from 1863 to 1869, where he championed native causes. He reorganised and codified old French system of law when he was the Administrator and Colonial Secretary of St. Lucia between 1869 and 1880. Afterwards, Des Vœux was appointed Governor of Fiji and High Commissioner Western Pacific from 1880 to 1885. He was appointed Governor of Newfoundland from 1886-1887. Based on his experience in British Guiana where he witnessed many instances of cruel and unjust treatment of indentured servants by plantation owners and managers, des Vœux wrote a 10,000-word report in 1869 to Lord Granville, the Secretary of State for the Colonies in which he detailed many abuses. When the contents of the report were published, there was a great outcry and a commission of inquiry was appointed, the Commission of Inquiry into the Treatment of Immigrants. Des Vœux gave testimony before the commission in Georgetown and its report led to many improvements in the workers' treatment.. How many years was Des Vœux  stipendiary magistrate and superintendent of rivers and creeks in British Guiana?