Constantius Chlorus rose from relative obscurity to become the Emperor of the western Roman empire. He was a soldier who had worked his way up through the ranks but his real political break came when in 289 he married Theodora, the stepdaughter of the emperor Maximian. By this time Constantius had already fathered a son called Constantine by another woman, Helena. Both Constantine and Helena went on to earn great renown in their own right.
In 293 the Roman Empire became a 'tetrarchy', meaning it was ruled by four different people. Constantius Chlorus was chosen by Maximian to be one of them - he became Caesar (junior emperor) of the northwest. This was a tricky assignment because much of the territory was in the hands of a break-away empire led by naval commander Carausius and his allies the Franks. That summer Constantius led a military campaign and regained control of Gaul, northern France. In 296 he did the same in Britain.
There followed nine years of relative peace which only came to an end in 305 when the Picts attacked the northern reaches of the empire in Britain. As so often in its history, York became an important strategic centre in a battle for the north of England.
Constantius was by now Augustus, the senior emperor of the west. He called for his son Constantine to join him in Gaul and together they headed to York. They enjoyed a series of victories over the Picts but then, on 25 July 306, Constantius became the second emperor to die in York.
Constantius’s first wife Helena became a saint after being credited with finding the relics of the true cross. St Helen’s Church and Square in York are named after her.
Their son became the next Roman emperor: Constantine the Great.