Markham was born in Ashwell, England, in 1902. She was the second child and only daughter of Charles and Agnes Clutterbuck. Charles moved the family to British East Africa near Njoro in today’s Kenya when Markham was four. Charles’s first love was horse racing, and he built a farm and ranch that eventually contained 100 horses. Agnes and the couple’s son, Dickie, moved away while Markham was a young child. Markham lived happily among the African population of the region, speaking Swahili, hunting with adults, and learning to train horses.

A severe drought caused Charles to lose the farm in 1919. He chose to move to Peru to train horses, while 17-year-old Markham remained behind, moving to Molo along the Mau Escarpment, where she built her reputation as a horse trainer. She soon relocated to Nairobi, where she continued to train racehorses until her late twenties.

After a chance encounter with pilot Tom Black piqued her interest in flying, Markham became the first female pilot in Kenya and perhaps in all of Africa. From flying mail bags and medical supplies, Markham moved into scouting animal movements for hunting parties. Eventually, she moved to England, where she accepted the challenge from Lord Carberry to attempt a solo flight from England to North America, which she accomplished in September 1936.