Y gwahaniaeth rhwng diwygiadau o "Yr Oriel Bortreadau Genedlaethol"

B
* 1917–1927 James Milner
* 1927–1951 Henry Hake<ref>{{cite web|url=http://www.rsc.org/delivery/_ArticleLinking/DisplayArticleForFree.cfm?doi=JR9300000888&JournalCode=JR|title=Cofiant i'w dad y cemegydd Henry Wilson Hake|date=1 Ionawr 1930|accessdate=12 Mawrth 2019|publisher=Rsc.org}}</ref>  
* 1951–1964 Charles Kingsley Adams[28]
* 1964–1967 Syr David Piper
* 1967–1973 Syr Roy Strong