I've dug to 2 different Borders. Handy dogs, but not out and out digging dogs. When I've quizzed my Grandad about his memorable days out there is always mention of more than one Border to ground. This will have been the 60s. I'm not crabbing their ways, it was all they knew. Different era and different outlook. I think that the Patterdale/Fell Terriers got lucky in that they landed roughly at the same time that the locators arrived and single handed dogs became the thing to have and obviously the rest is history.