My understanding is that this is a courtesy thing. So there is no legal requirement to do it.

I may be wrong though!

Agree with Anchorman - its generally accepted that the aris rails are visible on your side and not the neighbours, but it isn't a legal requirement. Maybe you should suggest that they erect their own fence within their own boundary alongside yours, since your posts and fence are on your land, and it is legally required that, if they wanted to grow stuff up the fence, they need to provide their own supports which are not affixed to your fence in any way. And not many people realise that one, common for people to attach mesh or trellis to the neighbour's fence, but technically, its illegal.

Do the new neighbours have nothing better to worry about than which side of the fence faces them! Oh dear!

It is usual to put this best side of your fence to the neighbours side, but the fence has been up twenty years so the new neighbours have to accept the fence as it is. You don't give any description of the fence but I would assume it is close boarded, feather edge and if it is on the left side of your property facing in from the front it is your fence. If the neighbours want a smooth side, feather edge boards can be put on the arris rail on their side with your permission.

Thanks for the replys. The fence consists of 4inch wide boards with a 2 inch gap between each board (6 foot high). When we errected all of our fences we put the posts on our side of the boundries and because there were originaly some hedges growing through the wire boundry fence all the boards were attached facing our side. Wouldn't care the house next door has been empty for 8 years or more!

As it is a picket fence and if the hedge has gone or just been taken out, your neighbours could put 4 inch boards on their side with your permission, to give the fence two face sides. Hope you can soon solve this.

Pity your neighbours have nothing better to do. Ignore them its your fence on your land, but after 20 years I would be wary of putting extra weight/stress on it as its quite an age now.

I had a similar problem. I put up a low front garden fence inside the boundary by an inch or 2. You can easily see it as a thin kerb stone runs down it. The neighbour painted 'his side' a different colour to mine. The fact he had to bend over a hedge to paint it must have given a clue to ownership (and he dropped the level in his garden), but as the smooth side is on my side, he claimed it was his. As everyone has said, there is no law that enforces that. The only boundary is one in the Land Registry and the like.

Quote; posts being on our side of the boundry fence.

As I see it;

This is the key part of your question!

This suggests the posts are on YOUR land,and now that you have fixed the fencing to the posts on YOUR side of the posts!

This means the fence in its entirety is on YOUR land so you can do what you want!

Which also would suggest because it is entirely on YOUR land your neighbour can not fix anything to it without your permission.

To do so can be construed as trespass.

It's all a bit tenuous but if you check your deeds you will find that it states that the " boundary fence is your responsibility" but there will be no details as to what the boundary is made of, but will say something to the effect that; "what it is made of will be properly maintained"

I think the 'best side' is only a courtesy thing not a necessity!

That's how I see it!