Palaeobiologists have unearthed the earliest evidence yet of hippos in the UK - at a cave in Westbury-sub-Mendip.

Excavations at Westbury Cave in Westbury Quarry led by University of Leicester PhD student Neil Adams, uncovered a million-year-old hippo tooth which shows the animal roamed Britain much earlier than previously thought.

In a new study published in the Journal of Quaternary Science and co-authored with researchers from Royal Holloway, University of London, the tooth is identified as belonging to an extinct species of hippo called Hippopotamus antiquus, which ranged across Europe in warm periods during the Ice Age.

It was much larger than the modern African hippo, weighing around three tonnes, and was even more reliant on aquatic habitats than its living relative.

Research demonstrates that the fossil is more than one million years old, eclipsing the previous record of hippo in the UK by at least 300,000 years and filling an important gap in the British fossil record.

Mr Adams, PhD researcher in the Centre for Palaeobiology Research at the University of Leicester and Earth Collections Project Officer at the Oxford University Museum of Natural History, said: "It was very exciting to come across a hippo tooth during our recent excavations at Westbury Cave.

"It is not only the first record of hippo from the site, but also the first known hippo fossil from any site in Britain older than 750,000 years.

"Erosion caused by the coming and going of ice sheets, as well as the gradual uplift of the land, has removed large parts of the deposits of this age in Britain.

"Our comparisons with sites across Europe show that Westbury Cave is an important exception and the new hippo dates to a previously unrecognised warm period in the British fossil record."

Scientists know remarkably little about the fauna, flora and environments in Britain between about 1.8 and 0.8 million years ago, a key period when early humans were beginning to occupy Europe.

But new research at Westbury Cave is helping to fill in this gap. It shows that during this interval there were periods warm and wet enough to allow hippos to migrate all the way from the Mediterranean to southern England.

Professor Danielle Schreve, Professor of Quaternary Science at Royal Holloway and co-author of the study, said: "Hippos are not only fabulous animals to find but they also reveal evidence about past climates.

"Many megafaunal species (those over a tonne in weight) are quite broadly tolerant of temperature fluctuations but in contrast, we know modern hippos cannot cope with seasonally frozen water bodies.

"Our research has demonstrated that in the fossil record, hippos are only found in Britain during periods of climatic warmth, when summer temperatures were a little warmer than today but most importantly, winter temperatures were above freezing."

By examining the European fossil record, the research team show that the Westbury Cave hippo was likely to have lived during a particularly warm period around 1.1 to 1.0 million years ago.

Hippo remains of this age are known from Germany, France and the Netherlands and the new fossil from Westbury-sub-Mendip represents a previously unknown part of this colonisation of northwest Europe.

This research was supported by the Palaeontological Association and the Natural Environment Research Council (NERC).

Researchers at the University of Leicester have previously discovered the first-ever evidence of an aquatic dinosaur, Spinosaurus aegyptiacus, and have investigated the relationship between humans and animals, dating back thousands of years.

'An Early Pleistocene hippopotamus from Westbury Cave, Somerset, England: support for a previously unrecognised temperate interval in the British Quaternary record' is published in the Journal of Quaternary Science.