I suspect that he is confusing the new series with the original series in which Volume 4 covered "Whernside and Gragareth" (subsequently split into Volumes 4A and 4B), and Volume 5 covered "The Northern Dales".
Sorry, sleep deprived self was referencing first series of Northern caves which had 5 volumes. I am needing second series which has three volumes only. Requesting volume 1: wharfdale and North East