Builder built garden wall 1.2 high outside of front boundary.

We believe, after checking land registry documents, the builder next door has built the front garden wall outside the boundary line of the property. Causing major visibility issues to driving out of our driveway,
it is a complete blockage of view.
the builder has been a nightmare from the start of the build and we believe this to be a way of annoying us further so contact with him is futile (self build, going on 4 years)
we have contacted planning who have told him to apply for retrospective planning as he originally had asked to put up a fence on that boundary.
we have contacted highways, no reply as yet.
we have no issue with him building a front wall, the issue is that it is not on his boundary. He cut half off the pathway up to put it there. Non of the villagers are happy about it but most fear the reproductions of saying anything so it’s up to us being the most affected to handle it.
surely he can’t ask for retrospective planning on something that he has built outside of his boundary, and causing Severe impairment of visibility to everyone using our driveway (we run a business so it’s in use all day every day)
as this issue is not The boundary between us (that’s a separate matter) we are not sure where else to turn for help correcting this?

Wendy - I'm sorry to read of the issues you are facing although there's very little we can usefully advise you on other than this is something to get legal advice on.
Whilst we can provide the registered information to confirm the registered extent/general boundaries and guidance on boundaries, this is very much something only you and the neighbour can resolve. If you can't then it's perhaps legal action you need to consider hence the legal advice suggested.
Planning issues inc retrospective permission is a matter for the local authority/planning department. We have no role in such procedures
If you are looking for wider online advice then there are forums such as Garden Law or Money Saving Expert where such matters are aired and shared and which may offer some help as to what has worked for others
But the properties, boundaries and neighbour are all unique to you so it is always legal advice that's recommended to ensure it's focussed on your unique set of circumstances

Thank you for that quick reply. We kind of knew this to be the case but hoping with the help of highways and planning this could be resolved under it being obstructive to residents so they will object to the retrospective application as well and a huge safety issue on the highways part so they will have to put it back into a non obstructive position (on their boundary)
thank you for the advice I will look into those places as well. Thank you for your help.