In the United Kingdom, ancient woodland is that which has existed continuously since 1600 in England, Wales and Northern Ireland (or 1750 in Scotland). The practice of planting woodland was uncommon before those dates, so a wood present in 1600 is likely to have developed naturally.
In most ancient woods, the trees and shrubs have been felled periodically as part of the management cycle. Providing that the area has remained as woodland, the stand is still considered ancient. Since it may have been cut over many times in the past, ancient woodland does not necessarily contain trees that are particularly old.