From the GW site blog:
I converted this about 10 years ago but never got around to painting it until about 3 years ago – this Looted Wagon (sometimes used as a Battlewagon with ‘Ardcase and Kill cannon) was converted using a Leman Russ and spare parts I and sitting around.
The idea came from the old Looted Wagon unit entry in an old Ork Codex. Ork generals could take tanks from other Codexes and use them in their Ork army. However, they were not quite as reliable; they were prone to exploding, driving off at random and firing their weapons unexpectedly. They were wildly unpredictable, inadvertently destructive and quite hilarious – perfect for Orks.
Although this unit doesn’t exist as a datasheet in Codex: Orks any more it does exist as a White Dwarf exclusive. Well, until now. Because we have it here for you to download and use for free!