Your spellchecker's given you the american spelling, the proper way to spell neighbour is with a "u" after the "o", so neighbour !

The plant looks a bit like a penstemons flower, google it and see if it looks right.

Sorry, my eyesight is not up to that. Could you get a clearer picture of the flowers and leaves?

It looks more like a wild flower to me....could be white comfrey.

I'd go for one of the comfreys too. the stems look hairy which penstemons are not.

Sorry about standard of photography Owdbody (not much good at it I'm afraid). Also had to lean over next door's fence to take it.

Louise1 - it was the spell checker on this site that I was following - never had much confidence in my spelling, that's why I pointed out that I suspected something was not as it should be. Now that I'm old and forgetful it's even more difficult trying to get things right. May I tentatively ask, should penstimons have an apostrophe? It was good of you to help.

Thanks Janey & Seaburn girl. Looking on Google seems to confirm your suggestion that it is probably White Comfrey

Well 'i' wouldn't put an apostrophe there, but i suppose some might !
There are some retired teachers on here .... they'd know the correct way of writing it !

Penstemon, or Pentstemon (both seem to be equally correct) would only have an apostrophe if you were talking about something which belonged to it. So one Penstemon, two Penstemons and the Penstemon's leaf was eaten
OK?
As I used to teach my class, if you never ever used an apostrophe again you would be more often correct than not!

It's definitely a Symphytum (comfrey) species, almost certainly a white flowered form of S. officinale, looking at the leaves and the shape of the flowers, and also given it's sudden appearance/arrival in your neighbour's garden.