His star cryptographer at SOE was Leo Marks, whose book Between Silk and Cyanide (1998) contains a detailed portrait of Gubbins and his work, as Marks knew it. At one point (p. 222), Marks describes Gubbins:
Described by Tommy [Marks' closest friend] as 'a real Highland toughie, bloody brilliant, should be the next CD', he was short enough to make me feel average, with a moustache which was as clipped as his delivery and eyes which didn't mirror his soul or any other such trivia. The general's eyes reflected the crossed swords on his shoulders, warning all comers not to cross them with him. It was a shock to realize they were focused on me.
Sir Colin's father, John Harington Gubbins (1852-1929), served with distinction as a scholar-diplomat in Japan for 30 years.