A friend has a 14 month old chocolate boy who has developed a frustrating new habit and favourite game, and is desperate for help! David (the pup ) is brilliant off the lead, very friendly with other dogs, but now loves nothing more than to steal a ball from another dog (chuck it blue and orange or Kong tennis balls are his kryptonite) in the hope of being chased. As my friend scrambles in embarrassment to retrieve the ball in front of the scolding owner, David takes great joy at darting away whenever she gets near. She's tried food lures or other balls but he's not interested in anything else. The major issue is actually getting him back on a lead to leave the park/fields/wherever he is and walk safely home. The only way to get him back is to walk away and he'll eventually follow. We've tried using my pup as a lure to get him to play with her, but he just wants the chase to continue. She's at her wits end with him and in desperate need of help in how to train a different behaviour. He's a big boy and needs a good run each day, it's just proving problematic when other dogs have something he wants. Does anyone have any experience with a similar issue or any pointers? Thanks!