There he was introduced to the South African High Commissioner Sir
Bartle Frere who sent him to the
Transvaal Republic which had been newly annexed by Sir
Theophilus Shepstone. There he would be initially appointed to its executive council. He entered the colonial secretary's office in
Pretoria and was private secretary to the new Administrator of the
Transvaal,
Sir Owen Lanyon, 1878–81. Lagden and Lanyon were in Pretoria when the town was besieged during the
First Boer War. After the war, Lanyon was recalled to London, but Lagden remained and was briefly private secretary to
Sir Evelyn Wood before returning to England in 1882. There he was engaged as war correspondent for the
Daily Telegraph in
Egypt, covering the British campaign against the
‘Urabi Revolt. He was one of a small party that entered
Cairo ahead of the main force to demand its surrender. He took part in the charge at
Kassassin and would deliver information essential to
Sir Garnet Wolseley in his efforts to harass the army of
Ahmed ʻUrabi and its eventual fall at the
Battle of Tell El Kebir. On his return in 1883, he was appointed Assistant Colonial Secretary in
Sierra Leone but was sent to do some brief work in the
Gold Coast. On the completion of the work there he was ordered to return to Sierra Leone by the Governor Sir
Samuel Rowe. He decided to take leave instead and visited
Kumasi, the first by a white man in twenty years, where he was captured and tried and he then escaped after being sentenced to die. After that, he fell out with the governor Rowe, and was sacked by the
Colonial Office. However, a friend he had made in Pretoria,
Marshal Clarke, had just been appointed resident commissioner in
Basutoland in 1884 and insisted that Lagden be re-engaged to work for him as his secretary, which he did and eventually succeeded Clarke as resident commissioner 1893–1901. In Basutoland, he managed to control the infighting between tribes in the country and succeed in establishing
hut taxes and their collection. During the
Second Boer War, which broke out in 1899, Lagden did all he could to keep Basutoland neutral ensuring the war did not draw in black soldiers. When he raised a force of 10,000 Basotho's and refused to use them to ensure the relief of
Wepener other than to watch over the
Cape Mounted Rifles, who were besieged by Boer forces until they were relieved by other British units. During the war, he raised and commanded the
Transvaal Light Infantry. In 1901 he was appointed commissioner of native affairs by
Lord Milner in the
Transvaal Colony, by then under British control and was also a member of its executive and legislative councils. During 1903 until 1905, he was chairman of the South African Native Affairs Commission and took evidence from all over South Africa and Rhodesia. ==Later life==