Charles Kao in Wikipedia
He did his PhD at UCL [1] in 1965 under Professor
Harold Barlow, as an external student while working at STL
His thesis was based on the optical communications project he was then
doing in the Laboratories
Note 1: University College London

Charles (Circled) as a member of Geoff
Dawson's group at STC Woolwich
Date: some time before 1960