I think a great deal of his reputation rested on him being an outstanding strategist. When he was at London Welsh, they seemed to be pretty well invincible. The Wales team of the 1970s was largely based on them, plus the Pontypool Front Row.
My dad was always proud of the fact that some pretty significant people followed him through the Lewis School, Pengam*. As well as John Dawes, there was Tony Lewis and Neil Kinnock. Not a lot to be proud of with the last one though...
*"The Winchester of Wales", according to David Lloyd George. Except, of course, it wasn't a fee-paying establishment.