Presumably the parish register was in Latin, so he wouldn't actually have been known as Radulphus; that was just the Latin version of his name.
According to the site linked to below, Radulphus was the Latin for Ralph but Ra
ndulphus was the Latin for Randolph, except in Shropshire and Cheshire where it meant Randall. Was yours definitely a Radulphus or could it be a Randulphus?
http://www.british-genealogy.com/res...latinnames.htm