Isn't it lovely the desire for a fast or easy buck wasn't allowed to win out? Pratchett's long term assistant Rob Wilkins was able to carry out the instruction nearly two and a half years after the authors death.
Nothing could be worse in my opinion than (perhaps a well intentioned) fellow author trying to second guess plot points and motivations or attempt to reproduce another's writing style. At least this way Pratchett's words remain untarnished and true in the minds of his fans.
In case anyone is interested, the Lord Jericho, a six and a half tonne steam roller at the Great Dorset Steam Fair was used. Wonderful.