sentences:  Returning to the Computer Laboratory in 1973 he resumed his work on the Rainbow integrated CAD system with the new PDP-11 computer and Vector General display.He attracted a great number of PhD students who went on to academic posts around the world and in research laboratories in Britain and especially on the West coast of America.In the 1970s he collaborated with David Kindersley MBE in the exploration of the mathematics underlying the aesthetics of lettering.