Born in England in 1867, Theodore Pennell was educated at Eastbourne College and qualified as a doctor (MB, MRCS, LRCP) in 1890, completing his MD and FRCS in 1891. He offered his services to the Church Missionary Society (CMS) in 1890. His father had died during his childhood, so he developed a very close relationship with his mother. When CMS sent Pennell to India, his mother decided to go too, and they both began learning Urdu. They reached Karachi in 1892 and went to Dera Ismail Khan, where Pennell began medical work. He often traveled round the villages, wearing Pathan dress and living with the people. He made his first visit to Tank in 1893 and established relationships with the Masud and Wazir tribes.