A building whose foundations were unearthed during an excavation at Marden Henge near Devizes last summer could have been a Neolithic sauna.

Archaeologist Jim Leary told his audience at Devizes town hall on Saturday that the chalk foundations contained a sunken hearth that would have given out intense heat.

“It brings to mind the sweat lodges found in North America,” he said. “It could have been used as part of a purification ceremony.”

Also found was a midden or rubbish heap with dozens of pig bones, some still attached, likely to be the remains of a huge feast that took place 5,000 years ago.

Mr Leary was supposed to give his talk at the museum, but such was the interest in his subject that it was transferred to the town hall. All 150 tickets were sold and people queued for returns.

Mr Leary said Marden Henge is the biggest henge in England but because it did not have a stone circle associated with it, tended to be overlooked. Before Professor Geoffrey Wainwright examined its northern sector in 1969, it had not been investigated since the early 19th century.

A huge mound, like a smaller version of Silbury Hill, named Hatfield Barrow, once existed there, but it collapsed after a shaft was dug through its centre and was levelled shortly afterwards.

The English Heritage team investigated that area as well as two sites further south, and it was at the area known as the Southern Circle that they made their most exciting discoveries.

It was in the bank of this henge within a henge that they found the chalk floor. Mr Leary described the dig as a work in progress. He said: “We are at a very early stage and there is a lot more to be found. But our fate is in the hands of the government cuts.

“Clearly there is more work to be done, at least another season, but we need funding to do any further investigation.”