Can I block off my side of a shared exit ?

[Treefella]

My neighbour and I created a shared vehicle exit between out 2 semi-detached houses around 25 years ago. (we both have an alternative means of exit that isn't shared.) This has the effect of giving each of us a sweep in and out drive with the middle exit being the shared one. Increasingly in recent times he has been obstructing the shared exit by allowing his callers to park their cars there. I have asked him on several occasions to keep it clear but he wont do so. Can I fence off my side of the shared exit so he no longer is able to drive across it, or indeed block it. I understand there are rules about easement. There is nothing on either sets of deeds about this shared exit.