I am not sure that he still is. I think he was/is a kiwi teacher who told Tim Martin he would never do anything with his life. Bit about him in the latest Wetherspoon News.
Right at the end of this 4min interview Tim Martin explains that his first pub was called Marleys in Muswell Hill. When the windows got smashed in by punters who were locked out on New Years/Christmas eve he changed the name on the replacement windows of the pub as a joke. Tim Martin said that he chose the name of his primary school teacher J.D. Wetherspoon because he couldn't control a class and Tim Martin decided he couldn't control a pub either.
I am sure there is a Kiwi accent in Tim Martin's speech. The sound quality of the interview is awful. Looks like it was a village hall production.
All of the stuff I've ever read about Tim Martin's choice of name for his company (including interviews with TM) has stated that it's only 'Wetherspoon' part that is taken from the name of his former teacher. The 'JD' bit is taken from the character JD Hogg, in 'The Dukes of Hazzard'.