Further groups of posts were seen further down the channel, suggesting other prehistoric wooden structures are present nearby.Analysis by a human bone expert showed that the female skull suffered considerably from gum disease and tooth loss. The ritual may have have been part of a Celtic ‘head cult’ which archaeologists suspect existed during the Iron Age, when people believed that the soul resided in the skull.Heads were often removed as trophies following battles and body-less heads appear frequently as motifs on art from the period.Excavations of Celtic earthworks have shown that skulls were routinely placed on display at the entrance to hillforts and religious places, such as the Iron Age shrine of Roquepertuse in France.The Greek historian Didorus Siculus also wrote of how Iron Age warriors embalmed the heads of their victims in cedar oil, and kept them in chests to show strangers. And it was said northern tribes hung the heads of fallen enemies on their horses before nailing them to their front doors on return from battle. Near to the skull, which was discovered near Newtown, archaeologists also found the remains of posts suggesting that a causeway or raised walkway once existed in the water. Iron Age warriors were said to collect the heads of their enemies. Credit: Heritage Image Partnership Ltd / Alamy Stock Phot When dog walker Roger Evans spotted a skull on the banks of the River Sowy in Somerset last March, police immediately suspected foul play.But the history of the mysterious severed head could be even more curious and sinister than originally thought.Analysis by experts showed that far from being the remains of a modern murder victim, the skull belonged to an Iron Age woman, aged around 45, who lived between 380 and 190BC.And gruesome cut marks show that she had been decapitated.Richard Bunning, an archaeologist from South West Heritage Trust, who has been excavating the site said: “We can’t tell if her head was severed before or after her death but it seems to be part of a particular kind of ritual because the head has been taken away from the body and deliberately deposited in a watery environment.“We have found similar severed heads like this in other watery places, so it seems that they were sacred places, rather than just where people were living.“We don’t know what happened to the rest of her body. We know that heads were revered in the Iron Age, and were of much greater interest than the rest of the bones.” Classical historians claimed warriors nailed the heads of vanquished enemies on to the doors of their roundhouses Credit:Jay Williams The woman’s skull was deliberately severed from her bodyCredit:Environment Agency Her diet included coarse material, which had unevenly worn her remaining teeth, and resulted in severe osteoarthritis in the joint of her right jaw.She had also suffered at least one episode of chronic illness or nutritional stress during childhood.“I think the skull is some kind of religious deposit,” added Mr Bunning. “We don’t know if she was a victim or a revered member of a tribe, but it was clearly an important ritual site.”Stephen Dean, Environment Agency archaeologist, said: “The chance discovery on the banks of the River Sowy has shone fresh light on Somerset’s hidden history.”The Environment Agency returned water levels to normal to provide a measure of protection to the timber posts and any other archaeological remains still in the channel. Archaeologists were able to study the site after the Environment Agency reduced water levels.Although no other human remains were found, the team discovered that the skull lay close to a series of round, timber posts driven deep into the river bed.Radiocarbon dating of the posts is being carried out to see if they and the skull are of the same date. Want the best of The Telegraph direct to your email and WhatsApp? Sign up to our free twice-daily Front Page newsletter and new audio briefings.