Reading the Philosophy page Stephen Paul KIng posted on Idealism (to catch up): Brand Blanshard (1892–1987) appears to have been the last of the English-world idealists, working in the 1930s.
“Knowledge must be knowledge of necessary connections, and reality itself must be an intrinsically intelligible system of connections or internal relations. Blanshard’s combination of the premise of the necessary isomorphism of knowledge and the known with the doctrine of internal relations exemplifies both an epistemological and an ontological argument for idealism”