I don't know what other advice you've gotten but 4 Dog Mother's advice about JP leaving your dog alone unless he's approached (and then letting London sniff and maybe giving him a treat) sounds good. Who feeds London? Maybe JP could try feeding him (if London will let him get that close). Most of the time dogs develop a bond with their primary caretaker, so if it were possible for JP to do these duties maybe London would learn to trust him. What a hard situation. Good luck.