"They only filmed the first book for the BBC, so I was kind of bummed out that they didn't do books two and three, so this time it would be nice to go back and do that as well," Hazeldine says. The BBC broadcast "The Tripods" as a television series in 1984, faithfully adapting the first and second books, but never getting around to a third season, which would've wrapped up the story. My guess here is that Hazeldine either didn't watch the second season or has completely forgotten about it. My own memory of "The Tripods" is hazy as well, my exposure to them being limited to a comic strip version of the books serialized in the pages of Boys' Life magazine.
Originally published in the late 1960's, "The Tripods" trilogy (The White Mountain, The City of Gold and Lead, and The Pool of Fire) relates the story of a post-alien invasion England, where man is enslaved by giant three-legged machines called Tripods. Humans over the age of fourteen are capped by the Tripods with an inhibitor that makes them into docile automatons.
The "uncapped" protagonists in the book are all pre-teens, which may mean that Proyas is looking to add a kid-friendly franchise to his resume. I liked Proyas' Knowing quite a bit, though I seem to be in the minority on that one, and I'm always up for seeing him take another crack at science-fiction. Wikipedia reveals that Disney acquired the rights to The Tripods series in 1997, and that Gregor Jordan (Ned Kelly) was once attached to direct for Touchstone, but Hazeldine made no mention of any attached studio, if and when The White Mountain finally sees production.