Researchers have discovered stone tools in Norfolk, UK, that suggest that early humans arrived in Britain nearly a million years ago - or even earlier.

The find, published in the journal Nature, pushes back the arrival of the first humans in what is now the UK by several hundred thousand years.

Environmental data suggests that temperatures were relatively cool.

This raises the possibility that these early Britons may have been among the first humans to use fire to keep warm.

They may also have been some of the earliest humans to wear fur clothing.

Image copyright Nature Image caption With the ancient tools were plant material, including a pine cone (top right) that provided clues about climate

The discoveries were made in Happisburgh, in the north of Norfolk. At the time there was a land bridge connecting what is now southern Britain with continental Europe.

There are no early human remains, but the researchers speculate that the most likely species was Homo antecessor, more commonly - and possibly appropriately - known as "Pioneer Man".

Remains of the species have been found in the Atapuerca region of northern Spain, and dated to 0.8-1.2 million years ago. So the species could well have been in Britain at around that time, according to Professor Chris Stringer of the Natural History Museum in London.

"If the climate was good and the land bridge was there, there's no real reason they couldn't have come (to Britain) as far back as 1.2 million years ago," he told BBC News.

Image copyright bbc Image caption One million years ago, a land bridge linked the UK to continental Europe

Pioneer Man was much like our own species in that it walked upright, used tools and was a hunter gatherer.

But physically the species looked rather different. It had a smaller brain, strong brow ridges and big teeth, with some primitive features such as a flat face and no prominent chin on the lower jaw.

'Real pioneers'

The discovery raises many new questions, such as how these creatures dealt with the cold winters that existed at the time. Scientists have also speculated that they may have used shelters and clothing.

It also raises the possibility that Britain was the first place where fire was used in a controlled way for warmth.

"Although we don't have the evidence for fire or of clothing to get through the winters up here, I think they must have had some extra adaptations," said Professor Stringer.

"I think the evidence suggests that they were living at the edge of the inhabited world in a really challenging environment and indeed they were real pioneers living here in Britain, nearly a million years ago," he said.

The research was led by Dr Nick Ashton of the British Museum, London, as part of the Ancient Human Occupation of Britain (AHOB) project.

Image copyright Other Image caption The discovery suggests that early humans may have adapted to the cold

"The discovery is immensely surprising because we are dealing with an incredibly early date," Dr Ashton said.

He added that the environmental data that indicated the relatively low temperatures was "even more surprising".

"It's unusual to find humans in such a cool climate this far north at this very early date," he said.

This area of Norfolk was quite a different place one million years ago.

"The [River] Thames was flowing through this area. And at the site we have sediments laid down by the Thames," he explained.

Pioneer man was eventually wiped out by an Ice Age. These occurred about every 100,000 years, and each time that happened Britain was depopulated.

As conditions became more benign, a new group of humans arrived.

There were at least eight different waves of people that came in and died out before the last wave, which is the one that survives today.