In message , Theo Markettos
writes

Another wild guess, but perhaps they're listed?

They are indeed. English Heritage ID 413898 shows that numbers 19-22
Leinster Gardens, "including 19a and screen wall forming equivalent of
nos 23 and 24" have Grade II listed status.

Most of the properties in Leinster Gardens are listed, and the entire
street is in the western part of the Bayswater Conservation area, so
development would not be at all easy.
--
Paul Terry