Around AD 55 under The command of Manlius Valens it moved to Usk, in an unsuccessful attempt to pacify the Silures, a tribe very resistant to the imposition of Roman rule in Wales.
But the legion suffered defeat, resulting in Valens’ replacement as legate[4] In AD 60 or 61 the Twentieth helped put down the revolt of queen Boudica, after outflanking the Ordovices it took part in the second Roman invasion of Anglesey which destroyed the Celtic Druids and their religious practices.
No further information is known after this period and scholars believe Legio XX was still stationed in Britain when Constantine III pulled the bulk of the military forces from there in the year 407 for his doomed campaign on the continent.
Legio XX Valeria Victrix and their final days in Deva (Chester) in the early AD 400s form the backdrop to the Tom Stevens mythic fiction genre novel The Cauldron (special edition)[23] with the story's protagonist Valerian—the Praefectus and Chief Centurion—defending the city with the rump of the legion against the incursions of Hibernian pirates as the "Dark Ages" settle on Britannia.
Legio XX Valeria Victrix was the legion featured in the novel Eagle in the Snow; author Wallace Breem postulates that they were annihilated by the Germanic invasion of 406.
Several of the main characters in the early novels of Jack Whyte's A Dream of Eagles series were former members of Legio XX Valeria Victrix.
Legion Company of the U.S. Army's 1st battalion, 503rd Infantry Regiment, 173rd Airborne Brigade stationed in Vicenza, Italy is named after Legio XX.