[1] Upon qualifying, during World War II, he joined the Royal Army Medical Corps in India,[2] and while with them became a Doctor of Medicine (DM).

[5] He served as secretary‐general (1965–1974, succeeding Guido Fanconi) and treasurer (1974–1977) to the International Paediatric Association, about which he also wrote a history, published in the last year of his life.

[1][6][7] Reviewing the book in 2008 Rolf Zetterström noted that it was "in some respects [...] more Stapleton's autobiography than a book about IPA" and credited him with "important contributions to paediatrics, such as the elucidation of a near-epidemic of hyper-calcaemia in infants, due to overdosage of vitamin D."[7] Stapleton was a co-founder of the European Society for Paediatric Research, in 1959,[7] and of the Neonatal Society.

[2] For many years collaborated with the China's Fourth Military Medical University, in Xi'an, hosting their students at Sydney (and later England) and in 2004, donating £200,000 to set up a scholarship there in his name.

[9] A memorial bench at Lane End commemorates his life, with a plaque noting that he "Helped improve the health of children around the world", in English and Chinese.