He doesn’t know how to behave around other dogs
Because of the excessive pulling, screaming, flipping over and freaking out when they encounter other dogs, they have tried all sorts of gadgets of ‘force’ I would call them. Contraptions to make Ivor unable to lunge, to force him to ‘behave’.
These have included a prong collar (disapproved of in this country), and various types of lead including an elasticated slip lead and ‘no-pull’ harness.