Sheila Mills was born in 1922, growing up in Norfolk, and was educated at Rhianver College and St James's Secretarial College in London. After working at a law firm she joined the Women's Royal Naval Service (WRNS) in September 1940 and served in Cairo, Alexandria and Suez and then in Germany after the end of the war. In Kiel she met Sub-Lieutenant Tom Unwin (1923-2012), a Czech-born intelligence officer with the Royal Naval Volunteer Reserve (RNVR) and they married in December 1946 after leaving military service.

In 1947 Tom Unwin obtained employment with the United Africa Company on the Groundnut Scheme, a project to cultivate peanuts in East Africa, and the Unwins lived in a tent in Tanganyika for three years. After the failure of the Scheme Tom Unwin joined the Colonial Service in Tanganyika and later worked in the Ministry of Foreign Affairs for President Julius Nyerere until 1964. Sheila worked when opportunities arose, including for the Head of the Groundnut Scheme in Kongwa and later for the British Institute in East Africa. Throughout her war service and while in Tanganyika she wrote regularly to her parents in England.

In 2006 Sheila published The Arab Chest, recording her many years of research into these collectors' items. Sheila Unwin died in 2009.