Richard Bartle
British game designer and academic who co-wrote the first MUD at the University of Essex, then spent a career explaining why people play in virtual worlds.
Roy Trubshaw started MUD in 1978 on a DEC-10 at Essex, and Bartle, then a first-year undergraduate, took over development when Trubshaw graduated in 1980. He expanded the world, the rules and the scoring. Because Essex had an early link to ARPANET, players from outside the university could log in, and MUD1 became the template for everything from AberMUD to DikuMUD.
In 1996 he published the paper Hearts, Clubs, Diamonds, Spades: Players Who Suit MUDs, which gave us Bartle's taxonomy, followed in 2003 by the book Designing Virtual Worlds. He is fond of pointing out that the MMO industry keeps rediscovering problems MUD players solved forty years ago.