Here is a photo taken in the roof space of a terraced house. Look twice. You can see directly into next door. This in itself isn’t unusual.
However, the underlining of the roof tiles/slates shows these properties have been reroofed. The white lining material in particular is modern, only having been widely used for about the last twenty years.
For as long as that most mortgage lenders have insisted that as a condition of a loan where a fire resistant party wall is missing between neighbouring properties it should be built up. This minimises the risk of fire spreading between properties and also restricts the number and amount of insurance payouts made.
So, why wasn’t this fairly basic requirement dealt with at the time of reroofing? Inconvenient now for buyer and seller alike.