Around 50 footprints, made by members by an early species of prehistoric humans almost a million years ago, have been revealed by coastal erosion near the village of Happisburgh, in Norfolk, 17 miles north-east of Norwich.
The discovery - made by a team of experts from the British Museum, the Natural History Museum and Queen Mary University of London - is one of the most important archaeological discoveries ever made in Britain and is of great international significance, as the footprints are the first of such great age ever found outside Africa. Indeed even there, only a few other examples have ever come to light – all in Kenya and Tanzania.
In Britain, the oldest footprint discoveries prior to the Norfolk finds, had dated from just 7,500 years ago, a tiny fraction of the age of the newly revealed examples.
The Happisburgh prints appear to have been made by a small group, perhaps a family, of early humans, probably belonging to the long-extinct Hominid species Homo antecessor ('Pioneer Man').
Archaeologists are now analysing detailed 3D images of the prints to try to work out the approximate composition of the group. Of the 50 or so examples recorded, only around a dozen were reasonably complete - and only two showed the toes in detail.
Tragically, although a full photogrammetric and photographic record has been made, all but one of the prints were rapidly destroyed by incoming tides before they could be physically lifted.
It's likely that the prints represent a group of at least one or two large adult males, at least two or three adult females or teenagers and at least three or four children.
The probable adult males had foot lengths of 25 or 26 centimetres - almost exactly the same as modern human adult males. The intermediate length feet (probably belonging to adult females or teenagers) were 18 to 21 centimetres long, while the probable children's feet were 14 to 16 centimetres long. Using the normal ratio of foot length to body height, this suggests that the individuals were a mixed group of adults and children, and were between 0.9 and more than 1.7 metres tall.
When they left their footprints, the group was walking across tidal mud flats at the edge of what, at that stage in prehistory, was the estuary of the Thames which flowed into the sea some 100 miles north of the present Thames estuary.
The group was walking upstream - away from the open sea, which was several miles behind them.
It's likely that they were searching the mud flats for lugworms, shellfish, crabs and seaweed - all of which would probably have been important food resources for them.
It's also possible that their home base was on one of the many islands in the estuary. And they may have been walking, at low tide, from such an island to the mainland. It's thought by some archaeologists that early prehistoric humans favoured islands for sleeping on - because that type of location dramatically reduced the threats posed by predators.
All 50 footprints were found on a small 40 square metre patch of former mud flat which had been buried for hundreds of thousands of years under sand and clay dumped there by Ice Age glaciers.
Archaeologists are now trying to determine the precise age of the footprints. They have so far succeeded in narrowing it down to two possible dates - around 850,000 years ago or 950,000 years ago. Only intense further study will reveal which of those two alternatives is the correct one.
However, scientific evidence - specifically ancient pollen - suggests that this prehistoric Thames-side stroll took place towards the end of a relatively warm so-called interglacial period, just before a resumption of Ice Age conditions. The climate had already begun to cool - and would have probably resembled that of modern southern Sweden, with night-time winter temperatures sometimes falling to as low as minus 15° centigrade.
The early humans who left the prints must therefore have worn rudimentary clothes in winter time - unless they had extremely thick and dense body hair.
It's not known whether they built basic shelters from wood and grass - but it's conceivable that they did. However, they probably did not have any knowledge of fire - as any frequent use of camp fires in Europe at that time would almost certainly have left archaeological traces. It's not known for sure whether these early humans had, by that time, developed the power of speech and language.
But they were definitely skilled tool makers - and archaeologists have found some 80 flint knives and scrapers from the Happisburgh site dating from this period. It's likely that they also used wood and other materials to make tools and other artefacts - but none have so far been found.
The early humans who left the footprints, lived in a hostile environment in which being eaten by big cats and other predators may well have been the major cause of death. Over the years scientists have found the remains of hyenas, lions, bears and sabre-toothed giant cats, dating from this approximate period at a variety of sites in Britain.
Evidence of hyenas (actually a lump of excrement from that species!) and scattered bones of elephants, rhinoceri, hippopotami, elk, deer, ringed seal and even sturgeon have been found within 150 metres of where the footprints have been discovered.
As the climate grew colder, the early human population either died out or retreated south to what is now mainland Europe. It is not yet known whether the footprint makers' species, Homo antecessor, became completely extinct - or whether it died out, but nevertheless contributed to the gene pool of subsequent species of early humans like Homo heidelbergensis which inhabited southern Britain in a subsequent interglacial period some half a million years ago or Neanderthal Man who lived 400,000 to around 40,000 years ago or indeed our own hominid species Homo sapiens.
"These footprints are immensely rare - and are the first examples of such great age to have been found outside Africa. They are of huge international significance because they give us a very tangible link to the first humans to inhabit northern Europe, including Britain," said British Museum archaeologist Dr. Nicholas Ashton, a member of the joint British Museum, Natural History Museum and Queen Mary University of London team which found the footprints and other traces of human activity at Happisburgh.
"As well as the footprints, we have also found the remains of substantial numbers of animals, including 15 types of mammal and 160 different species of insect - as well as more than 100 types of plant. This is allowing us to reconstruct, in considerable detail, the environment in which these early humans lived," said a leading expert in Ice Age mammals, Simon Parfitt of University College London and the Natural History Museum.
The 50 footprints discovered by the archaeologists and other scientists had been exposed last year at low tide as very heavy seas removed large quantities of beach sand from the site.
The prints were then recorded photogrametrically to produce 3D digitized images of them. Detailed analysis of the 3D images, carried out by Dr. Isabelle de Groote of Liverpool John Moores University confirmed that they were human prints. Geologically, they come from the same levels that had produced the flint tools and prehistoric animal bones in the surrounding area.
Prehistoric flint artefacts and other finds from the Happisburgh site, as well as images of the footprints themselves, will form part of a major upcoming exhibition, "Britain: One Million Years of the Human Story", due to open at the Natural History Museum on February 13.