The period in the British Isles, excluding Ireland, from prehistory to the Roman occupation. After the last glacial retreat of the Ice Age about 15,000 BC, Britain was inhabited by hunters who became neolithic farming villagers. They built stone circles and buried their chiefs in barrow mounds. Around 400 BC Britain was conquered by the Celts and 54 BC by the Romans under Julius Caesar; Boudicca led an uprising against their occupation. The original inhabitants gradually changed from hunting and gathering to keeping livestock and growing corn; traces of human occupation in the Old Stone Age have been found at Cheddar Caves, Somerset. In the New Stone Age the farming villagers buried their chiefs in long barrows; remains of flint mining can be found at Grimes Graves, Norfolk. In the Bronze Age they used round barrows. About 1800 BC, the Beaker people invaded, and left traces of their occupation at Avebury and Stonehenge (stone circles). About 450 BC the Iron Age began, and shortly afterwards Britain was conquered by the Celts, who built hillforts and left burial sites containing chariots. The Celts were a tall, fair- haired people who migrated in two waves from Europe. First came the Goidelic Celts, of whom traces may still be seen in the Gaels of Ireland and the Highlands; there followed the Brythonic Celts or Bretons, who were closely allied in descent and culture to the Gauls of France. The early Britons were highly skilled in pottery and metalwork. Tin mines in Cornwall attracted merchant sailors from Carthage. In 55-54 BC Julius Caesar raided England. AD 43 marked the start of the Roman conquest; among the most visible surviving remains are those found in Bath, Fishbourne (near Chichester), Hadrian's Wall, Watling Street, London (Temple of Mithras), Dover, St Albans, and Dorchester. In 407 the Romans withdrew, but partly reoccupied the country about 417-27 and about 450. For later history, see England, history; Scotland, history; Wales, history; and United Kingdom.