The advice given by Norfolk Boy is very, very important. Over many years I have been called into many boundary disputes, the cheapest loss to an outright loser I know of is �30,000 and two were in excess of �100,000. You are in an extremely serious situation with both your own and your neighbours houses now blighted and unsellable because of a boundary dispute. The dispute must be resolved by one or the other of you backing down in writing, it cannot be left open ended by one or the other "just going away". Remember also that however it is resolved the existence of the dispute must be disclosed to a future purchaser. It would be most unwise of you to provide your "neigbour's representative" with any documentation whatsoever. They will only pick over it see what can be twisted and used against you. Simply reply to the representative saying that to facilitate consideration you require fuller and better particulars from them of their claim against you. Depending on the reply, either give them the fence or engage a solicitor if you think they have no case. The position of posts, arriss rails, etc are no proof of ownership. The "T" on a plan shows whose fence it should be, but is not necessarily proof of ownership of what is there. I shouldn't say this, but if you are able to produce a plan showing the actual boundary 100mm your neighbour's side of the fence and get fierce about it that might get him to withdraw if he hasn't got much money.