Hi terrier1973,
Dont believe the old saying you cant teach an old dog new tricks, my first dog which i inherited was 9 years old and everybody said that she was great at hunting ,normally four drives in front lol. But i retrained her throughout the summer From scratch the same way as you would train a puppy only its quicker . I think most people would agree that to stop her from running in assuming she walks to heel of the lead and on ,is to use a check cord and every time she goes to run in stand on the cord and the dog will come to a halt and after a while they generally get the idea