Hunting 30yrs and one of the things I've learned, the hard way, is the dog game is full of snakes and spoofers. I hunt alone or within a tiny circle and stay well away from most of the 'dog men'.
There could be some way back, definitely a look of bull blood off him but fella I got him off doesn't know of it so it's way back in the breed somewhere if it's there.
Anyone looking for a ratting/bushing terrier to cover a bitch. I'm only want to use him to make sure his breeding is out there as I don't keep a breeding bitch at home, and I'd hate if something happened him and I'd none of his lineage around at working homes. All I'd want is a pup back from the litter or a future litter from his breeding.
He's patterdale x border/Russell. Excellent finding, marking digging rats. Very good bushing, flushing from cover, barks on scent fur and feather. Not a digging dog, doesn't go to ground. See him working in any of my posts.
Plenty of videos
Weather will play a big factor here, getting fox in holes. All you can do is put the miles in, walk the fields, woods, ditches, stone walls etc....... You will have some success, a terrier that be be hunted off the lead will improve your chances.
Some are very quick to condemn a dog. I'd agree with Corkman. Give young dog time and select their opportunities so that they will have every chance of getting a successful dig.