Article 4 directions are made when the character of an area of acknowledged importance would be threatened by development. They are most common in conservation areas.
An Article 4 direction removes certain rights that you would normally have to carry out certain works to your property, such as the ability to alter windows or construct extensions.
Where a property is affected by an Article 4 direction, you will need to submit a planning application before you start any works. A fee will be required.