There is a rebuttable presumption that a right of way marked on a definitive map actually exists, as marked. However, Section 53(2) of the Wildlife and Countryside Act 1981 empowers the local authority to MODIFY THE MAP if it discovers admissible evidence that there has been an error in its preparation.
Inconsistency between map and statement and/or comparison of the documents with the situation on the ground at the relevant time are such evidence. Indeed extrinsic evidence for this purpose is confined to that.