Sentence:  The degree of actual Dutch influence on the Norwich dialect is somewhat difficult to determine for the rather obvious reason that Dutch and English are closely related languages, both descended from <WSD>West Germanic</WSD>, and resemblances bewteen Dutch and forms of English are therefore most usually due not to the influence of Dutch on English, or vice versa, but to their common origin. 
Meaning of the word marked with <WSD> tags:  The presumed unattested ancestor of these languages (more properly called (Proto-West Germanic)).