The idea
If an occupant has lived in a property for 20 years they have the right to prevent the development of an extension to a neighbouring property if the extension will cause a minimal loss of light to a window.
Why is it important?
This law originates from the 12th century when natural daylight was extremely important inside buildings as the only source of light would be oil lamps or candle power. This law was last ammended in 1959 but now very much outdated.