More info in the media today about the Trefael Stone.......
Trefael Stone reveals stone age burial chamber
But it has now been reclassified after a survey established it as the capstone of a Stone Age ritual burial chamber.
The survey revealed the location, near Nevern, has been used for ritual burials for at least 5,500 years.
The first suggestion it may be more significant than one of Wales' many prehistoric standing stones was in 1972 when archaeologist Frances Lynch suggested it could be a dolmen, or burial chamber.
University of Bristol visiting fellow Dr George Nash and colleagues Thomas Wellicome and Adam Stanford held an excavation in September 2010 and returned again last year.
As well as unearthing the human remains, beads and pottery, they found a stone cist - a half-metre long coffin-like container - which they estimate was put there in the later Bronze Age.
The find indicates the site may have been reused as a burial location long after the original stone chamber was built.
Their findings suggest it may prove to be Wales' earliest Neolithic ritual burial location and one of the earliest in Western Europe.
Dr Nash said he knew of Lynch's 1972 comment on the stone, and that no geophysical survey or excavation had been carried out.
He said: "I've always had this hunch that it could be much bigger. It's extremely exciting. It's one of those once-in-a-lifetime finds."
The stone is already noted for a number cupmarks or circular holes gouged out during its ritual use in the Neolithic and Bronze Age ceremonies.
The archaeologists found a further 30 cupmarks of varying size on the 1.2m high stone.
Dr Nash said they were able to establish the site was stone burial chamber, built from giant boulders, going back to around 3,500 BC, which was then dismantled about 2,000 BC.
The capstone was then used as a procession marker standing stone pointing to nearby Bronze Age locations he said.