Rather than assume WHSmith where at fault, I checked with my distributor, Draft2Digital. They send my books to Kobo, who in turn send my books to WHSmith. D2D assured me the DRM was not being added by them and were distressed to hear that this was the case. Kobo haven’t replied to any of the messages in this thread: “WHSmith putting DRM in books distributed via Kobo”. I’m not holding my breath."
Link to Original Source