I also wonder from a water damage standpoint if he vented this or he’s counting on the door for ventilation. That won’t always be open.
Since the wall of this building is actually under the roof line, they’ll make him tear this down or reroof his house to move it four inches over (although that might take a permit too, since you’re changing the roofline). Tearing it down is cheaper.
He may also be violating setbacks from the edge of the property, but those have been diluted here so frequently in large cities that he might be okay.
Each member country of the UK have their own different planning regulations - Scotland, England, Wales and NI. Also please cite where having a shed next to your property is illegal in any one of these jurisdictions. Under certain dimensions and heights, planning "law" doesn't apply.
(I enjoyed the article.)