How long do longbarrows go back... intrigued by this thought went and found Ashbees "Earthen longbarrows" and heres what he says for Wayland Smithy.. This was excavated by Atkinson and he goes back to its primary start as an earthen longbarrow.
"as finally revealed, the evidence leaves no doubt that the burials were deposited within a wooden chamber resembling a low ridge tent, with a massive post at either end, between which a ridgepole was supported by mortised joints. The combined sides and roof were presumably formed of close-set timbers resting at their inner and upper ends on the ridge pole".....
Timber mortuary houses, or at least evidence of them are sometimes found in earthen longbarrows, timber did precede stone in all the monuments down here in the south west, and stone is only a later permanent remodelling idea of the symbolic use of these sites, be they, places to bury people OR shrines in their own right. One of the ideas for longbarrows has always been that they represented the house, but another equally so, is that they were symbolic of the earth. Neolithic people in their farming would quickly lose the fertility of the soil over a relatively short period of time, by representing the earth in a long barrow, or maybe even in Silbury hill, they were calling on their gods to fertilise the soil. Some of these earthen "longbarrows" extend to 150 ft, and must have had another reason for being built.....