He received his painting tuition at the Antwerp Academy of Fine Arts under Jozef Jacobs and Mattheus Ignatius van Bree.

When in 1855 the leading Belgian Romantic painter Gustave Wappers resigned as director of the Antwerp Academy, de Keyser succeeded him.

[1] He had many students, including Léon Abry, Aloïs Boudry, Edgard Farasyn, Godfried Guffens, Edouard Hamman, Joseph Lies, George du Maurier, Karel Ooms, Ferdinand Pauwels, Edward Portielje, Jan Swerts, Eliza Turck, Alexis Van Hamme, Jan Verhas, Frans Verhas and Charles Verlat.

Seeing the painting is said to have inspired the Belgian writer Hendrik Conscience to write his book "De Leeuw van Vlaanderen" (The Lion of Flanders) about the Flemish battle for independence from the French.

They chose as the subject matter of their work important historical events in Belgium's history which were regarded as key to the country's national identity.