Herbert Thoma was born in Munich on 31 March 1899, the son of Karl Thoma-Höfele, a painter who was related to the writer Ludwig Thoma. Herbert did his military service in 1917 and then attended Munich University to read German, English, History and Philosophy. In 1920-21 he was assistant to Hermann Paul, but was supervised for his doctorate (submitted in 1922) by Carl von Kraus, the great German medievalist and philologist. His doctoral thesis on Rittertreue was published in 1923.
After leaving university he went to work for the Süddeutsche Monatshefte, which ceased publication in 1936. In 1939 he left Germany for the UK to join his fiancée Susi Bauer, who had fled from Nazi persecution several years previously. Thoma was able to leave Germany on the pretext of travelling to England to research the early German manuscripts in British libraries as a supplement to the work of Robert Priebsch. To give plausibility to his trip, however, he was obliged to leave behind him all his personal and professional papers. Ironically, these were subsequently destroyed in the Allied bombing of Munich.
Once settled in England, Thoma married Susi Bauer and, through her good offices and those of a group of fellow exiles, he was approached by academics, including Professor Frederick Norman of the Department of German at King's College London, and persuaded to become an assistant in this department in 1947. In 1948 he was appointed Lecturer and, in 1950, became a Recognised Teacher in the University of London. In 1959 he was appointed Senior Lecturer. He lectured in medieval German language and literature generally but his special research field was early German glosses, on which he became a leading authority. He retired from King's College in 1967 but remained research-active until his death on 18 September 1975.