Between 1900 and 1910 Purnell lived and worked in China. In 1904 he and Charles Souders Paget (1874–1933), an American civil engineer from Bethlehem, Pennsylvania, established the architectural and engineering firm Purnell & Paget in Guangzhou (Canton).

Purnell designed many impressive buildings in Guangzhou, including the Arnhold-Karberg & Company building on the tiny island of Shamian (spelt ‘Shameen’ in his day), the competition-winning Imperial Customs House also on Shamian and the South China Cement Factory in Haizhu District. This was later requisitioned by Sun Yat-Sen for his headquarters.

At least a dozen of Purnell’s buildings still exist in China, including the three mentioned above. However, only recently has Purnell been ‘rediscovered’ by the Chinese and acclaimed as a major architect there.

Back in Melbourne, some of Purnell’s buildings appear to have been influenced by his years in Guangzhou. Some were for local Chinese clients, some had Chinese-style elements and some had Chinese names.