Turnbull's work is so foundational that a volume entitled "Studying Singapore's Past: C.M. Turnbull and the History of Modern Singapore" (2012), edited by Nicholas Tarling, was published in her honour, featuring contributions from leading scholars who reflect on and build upon her monumental contribution to the field.

Her academic contributions to Singapore's history were profound, beginning with her 1962 PhD thesis, later published in 1972 as This deep, scholarly work laid the groundwork for her grander, one-volume history.

The fall of Singapore to the Japanese Empire is treated as a critical turning point. Turnbull analyzes how the harsh Japanese occupation shattered the myth of European military invincibility, permanently altering the political consciousness of the local population and igniting early desires for self-governance.