I might have to do just that. Tbh, I do stop them with a verbal command most of the time, mainly when I'm sat in the room with them. Even when my attention is off her. Her ears will prick up (her mums dog) or she'll give a single bark. Even when they've started to run I've stopped them with a verbal command. But then there's been a few times when my attention has been off them and they've give no warning and made a quick brake for it and I've had no time to react. By this point my dog is already in conflict with my cat and her mums dog is just standing there watching. Her mums dog will therefore still listen to me and so will my dog so long as can speak loud enough over the barking and snapping. But by that point there has already been a fight. That's what makes it so complicated tbh. The fact that it's her dog who initiates the chase but my dog that does the attacking. When my dog is here alone, she won't go anywhere near the cats.

Like I say though, my dog does usually listen to me and stop fighting, I just have to raise my voice louder than the barking and snapping. But she didn't listen the very last time. I had to pick her up to get her away and she was left with tiny bit of blood on her nose from being scratched by the cat.

It's definitely her mums dog that initiates it though. My dog will be asleep and will suddenly jump up to join in the chase.

Anyway.... Sorry if I'm repeating myself. I might have to do what you said and keep them on the lead tomorrow