From the White Horse information board:
This famous landmark was probably cut into the chalk about 400 years ago, but its appearance has changed over time.
Local records from 1742 suggest that the horse was originally cut in the late 1600s, probably to commemorate the supposed Battle of Ethandun, thought to have taken place at Bratton Camp in AD 878.
In the 17th century, it had become popular to commemorate these supposed Saxon battle victories over the pagan Danes with white horses, in celebration of the belief that the Saxons had brought Christianity to Britain.
The tradition probably derived from the mistaken belief that the Uffington White Horse in Oxfordshire had been created in Saxon times to celebrate such a victory.
Cut into the chalk, the horse originally had to be scoured regularly to keep it white. The last recorded scouring took place in 1853. In the late 1950s, the horse was preserved by covering it in white-painted concrete.
The earthwork defences of an Iron Age fort over 2,000 years old — Bratton Camp — are still visible on the hilltop above the horse.
These earthworks protected a settlement, containing round houses, granaries, stores and workshops. The double banks and ditches may have symbolised the dominance and power of the hillfort community and would have been formidable obstacles to enemies.
Excavations within the fort in the 18th century by Jeffrey Whitaker, a local schoolmaster, uncovered quern stones, pottery, and Roman and Saxon coins. Also found were nearly a cartload of large pebbles, probably sling stones kept ready on the ramparts to throw at attackers.
3,000 years before, a Neolithic long barrow had been built on this hill. Still visible within the hillfort, it was preserved by the later occupants. Excavations into the barrow revealed human skeletons and cremations.
Bratton Down is designated as a Site of Special Scientific Interest (SSSI). This extensive area of chalk grassland supports herb and grass species that provide a habitat for a diverse assemblage of insects, including the rare Adonis Blue butterfly and the scarce forester moth.
The outline of the earth banks with the barrow in their midst can best be seen in the Google Maps satellite image.