Watch Digging for Britain Season 6 in Australia

We discover the camp from which Vikings invaded Britain, and find groundbreaking new evidence that the world-famous Avebury stone circle isn't just a sacred site but a place where our ancestors lived and worked - a discovery that's also changing our understanding of neighbouring Stonehenge. In Staffordshire, the oldest Iron Age gold in Britain is unearthed - a set of beautiful gold torcs, mysteriously abandoned 2,500 years ago.

We unearth the biggest collection of Roman writing tablets in Britain, giving insight into what Roman London was really like. Off the coast of Kent, we dive into the English Channel to complete the biggest marine excavation since the Mary Rose - an 18th-century East India Company ship, packed with silver. Also in Kent, we're on the detective trail to find the very first evidence of Julius Caesar's invasion of Britain - an ancient fort scattered with human skulls and weapons.

Alice discovers the well-preserved writing tablets, swords and domestic items left by Romans at Vindolanda during a time of British rebellion. On the Scottish island of Iona, there are traces of a long-lost monastery and pilgrimage site that was originally built by the legendary saint Columba, and has been compared to Jerusalem. In the east of Scotland, a weapons hoard belonging to a wealthy Bronze Age warrior is unearthed.

In this special, Professor Alice Roberts reveals the forgotten story of the Roman Army's secret weapon in Britain - their cavalry. These fearsome horsemen were the key to defending Britain's most famous Roman monument fortification, Hadrian's Wall. Alice sets off across Hadrian's Wall to investigate any evidence the Roman cavalry left behind, while a team of archaeologists and historical re-enactors attempt to re-stage a Roman cavalry tournament - a spectacle that no one has seen for over 1,600 years. We follow the team's training as they prepare for the performance, and Alice joins them at a public display in Carlisle where 30 riders perform in front of a crowd of spectators. To put the cavalry's story in context, the film also explores the latest archaeological digs happening across the UK, each of which is searching for new evidence of the Roman cavalry. On her journey across Hadrian's Wall, Alice visits some of the most iconic sites associated with the Roman cavalry, including Chester's Roman fort, Vindolanda fort and museum and Hexham Abbey. Along the way she builds a picture of the horsemen's lives here on the northern frontier of the Roman Empire.