Games Workshop Employee. Absolutely mutha fucking awesome.
His skill at writing rules and fluff are so great that they have shattered the boundaries of reality allowing him to write rules that actually affect real life (he has made himself WS BS Attack Initiative Leadership Strength and Toughness 10), however he has also has given himself an appropriate points cost, which prevents Games Workshop from taking him in their design team.
He only allows Matt Ward to continue existing because it amuses him.
Wrote a ton of the specialist games. Has a column in White Dwarf. He has given himself a holograph rule so GW won't keep bothering him with questions like "what rules should we give this?", "are we doing this right?" and "why are you so awesome?" while he's on one of his global thunderhawk tours righting wrongs and being cool.
He is one of The Four Gods of GW. Actually a lovely bloke who's been treated pretty shabbily by Games Workshop, probably because he sounds like an under appreciated butler character in a P.G. Wodehouse novel.
He and Phil Kelly seem to be the only GW employees that actually like the Eldar. And they are the most competent ones. Proof that intelligent people actually understand the Eldar and are capable of looking at both sides of a conflict, like any reasonable person would.
Interestingly, it was Jervis who revealed that the original idea behind deliberately obscuring the origins of two Legions of Space Marines (remember, in Rogue Trader, we had names for all 20) was threefold: a reference to the Teutoburg Disaster, as befits the Rome-themed Imperium, an opportunity for new hobbyists to create their own custom Legions for Epic and Apocalypse battles (which could potentially see more than a thousand Marines' worth of points employed) (although anyone who tried presenting their fluff for a missing legionne on /tg/ would get their shit righteously fucked up by fa/tg/uys), and to create a sort of 'holy grail' of untouchable fluff which no Black Library author could discuss, thus lending some mystique to the otherwise fucking goofy 2nd Edition fluff. Seriously, there was a canon character named Obi-wan Sherlock Clouseau.