From OpenStreetMap Wiki
Boundary of the Peak District National Park is now under blackadder 16:32, 9 May 2012 (BST). It was previously under Relation No. 78528 which was replaced in its entirety using the English Nature shapefile available since 2 April 2012 under the Open Government Licence. The old relation used many existing OSM features and these have been retained. The new relation stands alone and is not joined (as of the date of the import) to any other object. The relation is made up of 5 ways.