One of the requests I had was to introduce him to sheep and to use any method available to deter the impulse in him to chase.
I introduced the long line amongst other things but regrettably nothing worked. I was then forced to use an electric collar which did.
It should be noted that he ran very fast towards the flock and that without the collar he may well have attacked / chased an animal.
I appreciate that this is a controversial subject but believe that the alternative - having your pet legally shot by the landowner/farmer is far worse.
Suffice to say, a single use gave the result that was wanted and I was able to walk Duke for the remainder of his stay off lead, with sheep about.