4 year old gets very excited for walks and will start barking manically as soon as anyone even touches his harness. Recently, the barking just does not stop from the moment we put his harness on until we make it back home from the walk. He also pulls so hard and lunges in every direction. He's never been great on the lead but in the past 6 months it's got drastically worse (the constant barking is a relatively recent thing). We have had a behavioural therapist in to look at him and persisted with what she suggested to get him calm before we leave the house, but there has been absolutely no improvement whatsoever. He's very food driven at home, but couldn't care less about treats when walking and all he seems to want to do is bark 
Any help or advice massively appreciated.