This original semi-detached house was granted planning permission in 1975 and there was a condition imposed at that time that permitted development rights were withdrawn, this is usually the case when the house has been squeezed-in or is a sensitive approval, and the planners need to control any further additions.
The actual proposal is for a pretty simple addition to the rear of the house to widen the rear kitchen/dining room and we would expect would gain planning permission. We are at a loss as to why the agent in this case did not check the original approval, which would have informed the right approach to this application.