J. E. Wilkinson v. Ada Searls

"Extrinsic evidence of statements and declarations of the parties to an unambiguous written contract occurring contemporaneously with or prior to its execution is inadmissible to contradict, add to, detract from, vary or explain the terms of such contract, in the absence of a showing of illegality, fraud, duress, mistake or insufficiency of consideration." Point 1 Syllabus, Kanawha Banking and Trust Company v. Gilbert, 131 W.Va. 88.