DL postcode area
These districts cover central County Durham ( including Darlington , Bishop Auckland , Ferryhill , Crook , Spennymoor , Shildon , Barnard Castle and Newton Aycliffe ) , northern North Yorkshire ( including Northallerton , Bedale , Hawes , Leyburn , Richmond and Catterick Garrison ) and a very small part of Cumbria . 
<triplet> North Yorkshire <subj> County Durham <obj> shares border with