The context around this is the concept of the Right of Ancient Light. Under English law, windows that have enjoyed a sufficient level of light for at least 20 years are recognized as possessing a right to ancient light.

Once conferred, the owner of the property can invoke this right to prevent the construction of a building that would obstruct the level of light that enters these windows, or they can be compensated monetarily to give up this right.

The video doesn't explain this aspect, but the barriers were presumably set up so that his windows would never acquire this right, thus allowing the neighbor to develop their property sometime in the future without concern.