The Legend of Herne
Herne is said to have been a huntsman in the employ of King Richard II (reigned 1377–1399) in and around Windsor Forest. He saved the King's life when he was attacked by a cornered white hart, but was mortally wounded himself in the process. A local wizard brought him back to health using his magical powers, which entailed tying the dead animal's antlers on Herne's head. In return, however, Herne had to give up his hunting skills. The king's other huntsmen framed him as a thief. As a result he lost the favour of the king. He was found the next day, hanging dead from a lone oak tree. That same oak tree is in the Home Park at Windsor Castle.
The earliest written account of Herne comes from Shakespeare's The Merry Wives of Windsor in 1597:
Sometime a keeper here in Windsor Forest,
Doth all the winter-time, at still midnight,
Walk round about an oak, with great ragg'd horns;
And there he blasts the tree, and takes the cattle,
And makes milch-kine yield blood, and shakes a chain
In a most hideous and dreadful manner.
You have heard of such a spirit, and well you know
The superstitious idle-headed eld
Receiv'd, and did deliver to our age,
This tale of Herne the Hunter for a truth.
-- William Shakespeare, The Merry Wives of Windsor
This records several aspects of Herne's ghost which is said to have haunted Windsor Forest (covering all of East Berkshire and parts of south Buckinghamshire, northeast Hampshire and northwest Surrey) and specifically the Great Park ever since his death. Further details have entered local folklore from reported sightings , such as those in the 1920s. He appears antlered, sometimes beneath the tree on which he was hanged, known as "Herne's Oak", but more often riding his horse, accompanied by other wild huntsmen and the captured souls of those he has encountered on his journey. He is thus a phantom of ill omen, particularly for the country and, specifically, the Royal Family. He has a phosphorescent glow and is accompanied by demon hounds, a horned owl and other creatures of the forest.
(Source: Wikipedia but don't read that page as it contains spoilers for the adventure!.)