Barking on the lead at beginning of walk

[BuddyandFern]

Hi everyone, hope someone out there can help me... I am the proud owner of two beautiful border collies, one of which is a rescue dog. When I first adopted her she refused to walk on a lead through fear and was very fearful of people in general and we have made great progress, so much so that it is only when she meets strangers that I remember how far she has come and I am so proud! One issue we are still having is that when I take her out on walks she goes absolutely berserk for the first five minutes of the walk, barking like crazy! I've tried to distract her, have stopped walking waiting for quiet (which never came!) and I could really do with some good advice on how to handle things. Her tail is wagging and she is very "hyped up" so although she is fearful, I do believe she is excited rather than scared. She is also very protective of me, and my Mum says on occasions where she has walked her alone, she is no where near as bad. After 5 minutes or so she quietens down but does lunge and bark at other people and dogs. I would really love to resolve this problem as I feel this truly is the last obstacle that little Fern needs to overcome. Any ideas/advice would be gratefully received! Many thanks