[2] Jackson returned to Kenya in 1924 and settled there, learning how to grow coffee on a farm owned by Maxwell Trench near Nyeri.
Jackson established his own farm, Kapretwa, on the lower slopes of Mount Elgon and was joined by his father and other family members.
Jackson's farm was the first in the area to attempt to grow coffee but it quickly became one of the most productive in the Mount Elgon District.
[2] After the outbreak of war Jackson joined an officer cadet training unit and was drafted into the 4th battalion of the King's African Rifles.
[1] Following Operation Appearance, which liberated British Somaliland from Italian occupation, Jackson was assigned to the military administration of a large part of the north of the protectorate.
[2] Jackson returned to his farm after the war and continue to develop it, including a large garden featuring rare orchids.
In 1935 he participated in the British Museum expedition to the Rwenzori Mountains with the dipterist Frederick Wallace Edwards and the botanist George Taylor.
[4] Jackson developed new techniques of capturing and breeding the insects and trained black staff who collected specimens for him in Kenya, Uganda, Tanzania, Middle Congo, Cameroun, Nigeria and the Ivory Coast.