In his 2003 book, Harold Innis, Paul Heyer describes the relation of Innis and Havelock as follows:

Havelock’s importance [for Innis] was due to the interdisciplinary vision he shared with Innis, which eschewed any hard-and-fast division between the humanities and the social sciences, and because of his interest in the interplay between power and and knowledge in historical change. It has been argued [Heyer cites Watson here] that Havelock eventually became more indebted to Innis than vice versa and that his work is an extension of Innis’s take on Greek civilization, the alphabet, and the social consequences of technological change in communication media. Since Innis’s death Havelock has written extensively on these subjects — in ways that have significantly influenced Marshall McLuhan — but he has attributed  the similarity between his project and Innis’s to “a matter of happy coincidence”. (42)¹

Like Watson, Babe and Carey, Heyer sees no significant tie between the communications work of Innis and Havelock while Havelock was at UT and any influence between the two as extending from Innis. And like Babe, he sees the influence of Havelock on McLuhan operating only “since Innis’s death”. Neither view seems tenable.