Thanks Harm. Just to say, I've just used RegisterNavigateForwardPath in a different (class based) scenario and it helped me out a lot.

My original scenario that caused the post actually turned out to be a non-issue in the end, because all 4 instances of the class were all inside the same webview object, meaning that the callback object was always the same, so adding a single WebRegisterPath entry inside that view was all that was required.