He died in 1948. Fonseka was much praised for his inspiring teaching and dedication to his work. Among his pupils was the novelist Ambalavener Sivanandan, who recalled that Fonseka "really stimulated me...De Fonseka gave me a taste for language: English sat on my tongue, I could taste it together with the Tamil I spoke at home." He also mentored the Sri Lankan artist and advertising mogul Reggie Candappa, getting him his first work as an illustrator.