Knock on his door !!
Explain about the fence - taking with you your deed copy to show him and explain that if he was wondering why a new fence had not been put up it was because your not responsible for it he is.
For some reason people dont talk to their neighbours and always think that it will turn into a fight or an argument - 9/10 just go and ask them round for a beer or a cup of tea to discuss the fence. You could always put one up on your side of the boundary - I couldn't be doing with no boundary - anything's better than nothing.