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Archaeologists have unearthed evidence of the earliest large-scale celebrations in Britain - with people and animals travelling hundreds of miles for prehistoric feasting rituals.

The study is the most comprehensive to date and examined the bones of 131 pigs - the main source of meat for the feasts - from four Late Neolithic complexes.

Serving the world-famous monuments of Stonehenge and Avebury, the four sites - Durrington Walls, Marden, Mount Pleasant and West Kennet Palisade Enclosures - hosted the first pan-British events, feasts which drew people and animals from across the country.

The results show that pig bones excavated from these sites were from animals raised as far away as Scotland, the North East of England and West Wales, as well as numerous other locations across Britain.

The researchers believe it may have been important for those attending to contribute animals raised locally at their homes.

Before now, the origins of the people who took part in rituals at these megalithic monuments and the extent of the population's movements at the time have been long-standing enigmas in British prehistory.

Study lead Dr Richard Madgwick, from the University of Cardiff, said: "This study demonstrates a scale of movement and level of social complexity not previously appreciated.

"These gatherings could be seen as the first united cultural events of our island, with people from all corners of Britain descending on the areas around Stonehenge to feast on food that had been specially reared and transported from their homes."

Representing great feats of engineering and labour mobilisation, the Neolithic henge complexes of southern Britain were the focal point for great gatherings in the third millennium BC.

Pigs were the main animal used for food and they provide the best indication of where the people who feasted at the sites came from as almost no human remains have been recovered.

Using isotope analysis, which identifies chemical signals from the food and water that animals have consumed, the researchers were able to determine geographical areas where the pigs were raised.

The study offers the most detailed picture yet of the degree of mobility across Britain at the time of Stonehenge.

Dr Madgwick added: "Arguably the most startling finding is the efforts that participants invested in contributing pigs that they themselves had raised.

"Procuring them in the vicinity of the feasting sites would have been relatively easy.

"Pigs are not nearly as well-suited to movement over distance as cattle, and transporting them, either slaughtered or on the hoof, over hundreds or even tens of kilometres, would have required a monumental effort.

"This suggests that prescribed contributions were required and that rules dictated that offered pigs must be raised by the feasting participants, accompanying them on their journey, rather than being acquired locally."

- The study, Multi-isotope Analysis Reveals That Feasts In The Stonehenge Environs And Across Wessex Drew People And Animals From Throughout Britain, is published in the journal Science Advances.