The Man in Black
A man who looked similar to the Man in Grey but wore darker robes was once active in the same universe as a balding man wearing a floral shirt who sometimes went by the name “Fred”. The Man in Grey was aware of this similarity, though its significance was unclear. Doctor Know compared it to his own similarity to “the time-traveller guy”. The Man in Grey was keen to keep it a secret from the Great Higher-Ups, and Doctor Know blackmailed him into giving Know a job at the Multidimensional Finders Service by showing him photographs of the man in the dark robes. (PROSE: Open Sourcing)
Behind the scenes
The “darker man in grey” is strongly implied to be the Man in Black featured in Callum Phillpott's own earlier novel, Cyber-Hunt, set in the Doctor Who universe to whom the Man in Grey was indeed suspiciously similar. Unlike the Man in Grey, his DWU equivalent was not an open-source character.
