The right of way will appear in the title deeds to your and his property and a local conveyancing solicitor can get a copy for a few pounds.
The deeds may have an actual measurement of the boundaries or they can be calculated albeit roughly for the index map which is to scale. I would then threaten an injunction if he fails to restore the easement/ right of way. You can also claim for your legal costs to be paid provided he is warned that you will take court action should he fail to comply.
I think that covers it but let me know if I have missed something.