You know what, mate, and I'm totally serious here. I remember your Hancock bred dog, AND my son has owned a 3/4bred from him, a few associates of mine have owned dogs from him, plus I owned a dog sired by taffy, one of his stud dogs, to a locally bred very greyhoundy mongrel lurcher bitch, and NONE of them have been slow. All catching hares pretty regularly.
Not saying you did, but did you try your dog on a hare when he was a bit too young, and not quite ready?
There's a BIG difference between a rabbit's speed and a hare's speed.