Although Britain was occupied for hundreds of thousands of years, the pre-Celtic era we’re talking specifically about is the Neolithic period, which begins around 4300 BC. The Neolithic peoples of Britain and Ireland are set apart from their ancestors because they began to exhibit an increasing control over their environment. They were farmers and herders; they had villages; and they started building religious monuments, what archaeologists call ‘neolithic monumental architecture’. This includes burial mounds, stone circles, and standing stones, all of which were part of what we would view now as their ‘religious’ system.
Unfortunately, we have no written documents dating to this time, so can only use evidence from the monuments themselves and artefacts that survived to make informed guesses about what prehistoric people actually believed. While there was no single or continuously developed belief system in prehistoric Britain, they appear to have had extensive religious practices relating to the burial of the dead and a belief in the afterlife.
Evidence for these beliefs has been laid out physically for us to see and developed over a four thousand year period in the building of what English Heritage calls “ritual landscapes”. To create these landscapes, the people of Britain constructed barrows, which are mounds, either long or round, in which the dead were buried; burial tombs on the tops of hills; stone circles like Stonehenge; and other standing stones, all of which were set physically apart from normal, village life. Many, if not most, of the sites that have survived were oriented to the sun, moon, or stars.