From the middle years of the 19th century, many local councils took advantage of new powers available to them to require developers to submit plans for approval before building could take place. The extent to which these plans survive varies greatly from area to area; some plans remain with council planning departments or borough engineers, and many have been lost or destroyed over the years. Good collections of plans (or microfilm copies of them) can however be found in many local record offices. They can provide exceptionally good evidence of how nineteenth century buildings might have looked when new.