Following completion of his studies at Stedelijk Gymnasium Nijmegen, Gumbert went on to read classics at Leiden University where he met his wife, the classicist Marijke Hepp.
[3]: 9 An internationally recognised authority on the medieval book, Gumbert was invited to take up research scholarships at multiple institutions throughout Europe, as well as in the United States and Israel, but elected to remain at Leiden.
[3]: 6 He sat on the editorial boards of numerous academic journals and scholarly series, organised several informal circles devoted to codicology and palaeography,[3]: 10 [4]: 23 and acted as both treasurer and committee member for the prestigious cipl, Comité International de Paléographie Latine, for half a decade.
In addition, he co-founded the academic journal Gazette du Livre Médiéval, and helped establish apices the Association Paléographique Internationale — Culture, Écriture, Société in 1993.
[5] A prolific and well-respected scholar, he published individual research and editorial works in multiple languages including Dutch, English, French, and German.