DoB comes from John Black's copy of the CWGC list of internees, which gives Mr Jones's occupation in 1941 as "Draughtsman".
Mr Jones is listed on page J114 of the 1939 Blue Book as one of the two Chief Draughtsmen in the Public Works Department, first appointed to the Hong Kong Government on the 3rd Jan, 1939.
In 1943, while interned in Stanley Camp, E I Wynne-Jones (the Postmaster-General) asked him for help. Wynne-Jones had made a rough design of a stamp to be used to celebrate the eventual end of the war, and wanted Jones's help to make a better drawing. The designs were used after the war, to produce these stamps in 1946:
You can read more about WE Jones and these stamps in the article: Hong Kong Stamps – Victory Issue SG.169 & SG.170.