For 1,900 years the secret of Rome’s missing Ninth legion has been shrouded in mystery, its ultimate fate argued over by generations of historians. We reveal how the loss of the Ninth legion was a truly catastrophic event: the devastating news was suppressed by Hadrian to safeguard his reign in a classic conspiracy cover up. It was the first in a chain reaction of disasters which forced Rome to halt expansion and to create the only two massive frontier walls ever built in the Roman Empire. Written sources and a raft of new archaeology show how and where the Ninth met its end in the tribal badlands of northern Britain. In a stunning reveal archaeologists show how Hadrian built a huge innovative timber rampart to protect Roman forces before his monumental stone wall and later sent his best generals including the infamous Julius Severus, a ruthless soldier who perfected devastating new tactics against insurgents. But beyond the frontier, tribes formed powerful new alliances and harried Roman military in a guerrilla war of attrition. Over fifteen wars were fought. Three Roman generals and an estimated over 20,000 troops died fighting hostile tribes while vast resources were ploughed into trying to maintain the vulnerable frontier system. The might of Rome was waning - the annihilation of the Ninth was the writing on the wall. This was the beginning of the end.