So I'm sitting here photographing and cataloging some of my coins - mainly third century Roman Imperial coins, but heavily dominated by the breakaway Gallic Empire of Postumus, Victorinus, Tetricus I and Tetricus II (260-274AD).

I have collected them for over 25 years, but even now I am learning from them as I handle them, turn them and weight them in my hand. Every Emperor is different, but each coin and indeed each strike, mint, style and type tells you something - whether what we learn is fixed and firm varies, but there is much than can be garnered and relied upon. Let me start with the Emperor Postumus.

So students of Roman History tuck into Suetonius: Lives of the Ceasars. It is gory, gruesome, almost red top in modern newspaper style. But upon analysis the facts often ring true.  The characterisation and the stereotypes are over-vivid, but it is at least semi-contemporaneous gossip and rumour.

Indeed, I am always minded of my historical muse, mentor and inspiration Peter Connolly. "Why read novels, when you can read Suetonius?"

Some periods of history stand out, others are unknown. Some achieve landmark status - take Roman Britain as an example. 55BC is known as the initial invasion of Britain by Julius Caesar, 43AD as the successful invasion of Britain by the armies of the Emperor Claudius, and 60AD as the rebellion of Queen Boudicca of the Iceni.

The end of Roman Britain is much heralded as being dated to 410AD, but this is probably misleading and misrecorded. And some other key events are well known, but the dates less so - folks know about Hadrian's Wall, they know about Roman Londinium, and that Constantine the Great was declared emperor in York. Occasionally, people are aware of another wall north of Hadrian's Wall called the Antonine Wall.

So if this Gallic Empire broke away from Rome but essentially failed and lasted a mere 14 years why is it so interesting and so compelling? Surely it's just another grubby rebellion that litters Rome's history and adds to the notion of a decline in the Third Century? In part it was grubby and unsuccessful, but in other regards absolutely not. I will argue that in fact the Gallic Emperors were the very reason The Empire that was Rome was able to survive.

The context was that Rome as an Empire was in trouble. The rise of the Sassanian Empire was relatively new (c.240AD) but crucially it was real military threat and achieved early success under Kings Ardashir and Shapur I. The Emperor Gordian III had lead a major war against the Sassanian Kings and lost, losing his own life, probably in battle and the successor Emperor Philip I had to pay a significant financial tribute to achieve peace, fix Imperial borders and to withdraw the battered army.

A story that has been largely ignored in the chronology of the Roman Empire is the creation in 260AD of an independent empire covering the western provinces of the Roman Empire.  Led by the Roman Emperor Postumus, the Gallic Empire survived for 14 years.  Resisting barbarian attacks, free from the politics and taxation of Rome it comprised modern day Spain, Portugal, Britain, Belgium and France and lower Germany.

The story is a rich one and the names of the emperors are not just dry dusty lines in the annals of the Roman Empire.  We have their names, wives, families, personal stories and anecdotes, archaeology, inscriptions and yes, even portraits - fine art indeed - of the very faces of these Emperors.  We know who they were, where they lived and what they looked like.  Unlike the early Kings of England - we can see the very faces of these Emperors from 1800 years ago