In article , Wig wrote:
I'd be surprised if they got planning permission to build up to and
on top of the party wall/boundary line. My council would never have
granted this, I know because I asked them.

The fact that what is proposed is not on your own land is not a reason
for refusing PP. You can apply for permission to do something on a site
that you do not own any part of - most usually done as a prospective
purchaser, but I have known a local environmental group do this to
establish the fact that site x could be used for y, and not turned into
flats.

The only restriction is that if your application is for, or includes,
land which you do not own, you have to serve a notice on the owner of
said land. The fact that such as notice has not been served will not
generally invalidate any permission that has been granted (except in the
case of fraud), but it does render you liable to being prosecuted, and
of course the fact that you have PP does not give you any rights to
build over your boundary.

In this case if the wall has been built over the boundary then ISTM
(IANAL) that the adjoining owner has two choices: rebuild it on his side
of the boundary, or accept it as a party wall.

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