The Hatley Heart Attack was a loop of 400+ caches starting in Hatley and heading north east up to Toft before heading south, then south west all the way over to Biggleswade before heading back up to Hatley.
Most tracks are easy walking with a little road walking sometimes needed. There were numerous link caches to break the walk into smaller more manageable chunks. But did anyone walk the outer ring in one go?
Check out the BookMark List for a complete list of the entire series plus link caches.