MacDermott was born in Plymouth, Devon, United Kingdom. Her father was a surgeon with the Royal Navy and her mother was a teacher. Due to her father's work in the navy, she spent some of her early years in Weihai, China, where Mercia learned Mandarin Chinese. She was educated at Westonbirt School, Gloucestershire and Oxford University where she read Russian philology. In the summer of 1947, while participating in a youth brigade in Yugoslavia with other English students, she first met with Bulgarians, among whom was the writer Pavel Matev.
In the same year, MacDermott visited Bulgaria for the first time to attend a celebration at the Divotino brigade members camp near the Pernik–Voluyak railway line. In 1948, she graduated at Oxford and once again visited Bulgaria to participate in the international youth brigade building the Koprinka Reservoir. As a foreign udarnik, MacDermott was invited along with other international participants to meet Georgi Dimitrov in the Euxinograd palace on the Bulgarian Black Sea Coast. While working at the Koprinka reservoir, Mercia met her future husband Alexander MacDermott. Returning to the United Kingdom in 1948, MacDermott enrolled in a Bulgarian language course at the University of London's School of Slavonic and East European Studies.
MacDermott resided in Bulgaria from 1962 to 1989 with brief interruptions. From 1963 to 1979 she was a teacher at the Sofia High School of English. MacDermott subsequently attended lectures on the Bulgarian national liberation movement in the region of Macedonia at Sofia University's Faculty of History. She was elected a foreign member of the Bulgarian Academy of Sciences in 1987 and was granted a doctorate honoris causa by Sofia University in 2007.
MacDermot's activity is descibed by Waller, Diane (2000) in "Black Lambs and Grey Falcons", Oxford, Berghahn Books, pp. 166 - 186, "Mercia MacDermott: A Woman of the Frontier", Allcock, John B. Antonia Young (eds.)
Positions and awards
From 1958 to 1973, MacDermott was the chairwoman of the London-based English–Bulgarian Association. An honorary citizen of Karlovo and Blagoevgrad, she is also the bearer of a number of Bulgarian state decorations.
The MacDermotts had a daughter, Alexandra MacDermott (b. 1972), now a nuclear physicist.
- A History of Bulgaria 1393–1885, Allen and Unwin, 1962, OCLC 279468
- The Apostle of Freedom (A portrait of Vasil Levsky against a background of nineteenth-century Bulgaria), Allen and Unwin, 1967, OCLC 957800
- Freedom or Death (the life of Gotsé Delchev), Journeyman Press, 1978, ISBN 978-0-904526-32-5
- For Freedom and Perfection (the life of Yané Sandansky), Journeyman Press, 1988, ISBN 978-1-85172-014-9
- Bulgarian Folk Customs, Jessica Kingsley Publishers, 1998, ISBN 978-1-85302-486-3
- Explore Green Men, Heart of Albion Press, 2006, ISBN 978-1-872883-94-6
- Lone red poppy, Manifesto Press, 2014, ISBN 978-1-907464-10-2
- Once upon a time in Bulgaria, Manifesto Press, 2016, ISBN 978-1-907464-16-4
- Allcock, John B.; Antonia Young (2000). Black lambs & grey falcons: women travelling in the Balkans. Berghahn Books. p. 168. ISBN 978-1-57181-744-0.
- For Freedom and Perfection. The Life of Yané Sandansky. www.kroraina.com. Retrieved 26 March 2012.
- Allcock, p. 173.
- Макдермот, Мерсия (1979). Веселин Измирлиев, ed. Свобода или смърт: биография на Гоце Делчев (in Bulgarian). София: Наука и изкуство. OCLC 82956003.
- See Foreign Members of the Bulgarian Academy of Sciences