For the past three years Case’s massive Quadtrac has been keeping the Caterpillar-built Claas Challenger company in the UK’s 300hp+ rubbertracked sector. But that crawler company is in danger of becoming a crawler crowd – should John Deere decide to join the high hp tracked party and sell its 9000T on this side of the Atlantic, too. Andrew Faulkner travels to Iowa for a tour of Deere’s flagship tracklayer