Question Author
Update:
So, after speaking to person B and her dad on the phone last night, person B changed her story completely and said it was not her dad but person A and her family who forced her to give the dog up. Then she changed her story again and said she didn't know she was giving him up (even though she bought all his belongings and told me how to get him re-registered to us).
My partner was speaking to her as i was too upset, and after about 20 minutes of going round in circles, spoke to her father who threatened to break into our house and take the dog back, then threatened to kill my partner...call was terminated by us and the police were duly called. Police were shockingly unhelpful. They said they would note that threats of death and violence had been made but said ownership of the dog was a civil matter. Person B and her family could take us through the small claims court and may be given the dog back, but realistically we could face months of verbal and physical harassment from these people and was it really worth it?
It is with a heavy heart that we have decided it will probably be best to give the dog back to person B and move on with our lives. My partner and I are decent, educated people and we don't need this in our lives.