Dredd was filmed on location in South Africa, and took advantage of some of the country's more downtrodden locations (as well as cheaper local crew members and a 25% tax rebate). So why not also take advantage of some of the country's local acting talent? Book of the Dead is one of 2000 AD's few stories to feature the Pan-African Judges, who police the continent which has become more isolated following the wars that irradiated their deserts in the same way as Mega-City One's Cursed Earth. An early work by one Grant Morrison - I think he went on to some bigger things - Book of the Dead is pretty campy as far as Dredd storylines go, which isn't really in-keeping with the grim and gritty tone of the first film. The location, however, is interesting, as is the opportunity at a more diverse cast of characters, and again to expand the universe outside of just post-apocalyptic America.
Tom Baker is the Comics Editor at WhatCulture! He's heard all the Doctor Who jokes, but not many about Randall and Hopkirk. He also blogs at http://communibearsilostate.wordpress.com/