My meagre follower count is getting up towards the years when King Arthur "may have" existed (but almost certainly didn't). So I think I'm going to tweet whenever we reach a fun year.

430 AD was the year when the Vandals sacked Hippo Regius, in modern day Algeria. That hasn't got much to do with Arthur on the face of it, but in my novel Hector's father (and Kay's grandfather) fled the Vandals and ended up in Britannia with nothing but the shirt on his back.

Hilariously I lost followers after tweeting this. I hope we don't go too far back in time.

Well I appear to have dropped down to 428 followers. So I'm going to use that as an excuse to talk about Vortigern and the Saxons, because - according to the Historia Britonnum - 428 AD was when Vortigern invited the Saxons into Britain, to help him with his Pict problem.

The arrival of Saxons, Angles, Jutes and Frisians in Britain was probably a slow process of migration and peaceful settlement rather than a sudden invasion or invitation. Susan Oosthuizen's 'The Emergence of the English' is a great book about this for anyone interested.

Warriors from modern-day Denmark and Germany were often hired as 'foedarati' (mercenaries) during the late Roman Empire, so this probably continued into the fifth century. The last Roman legions left Britain in the 410s and may have been supplemented by more and more mercenaries.

But this isn't how it was remembered by British writers of later centuries! The Historia Britonnum - written or compiled in 828 by a Welsh monk called Nennius - depicts the arrival of the Saxons as a single event, ushered in by an evil king called Vortigern

Now Vortigern gets a very bad rep in most early histories of Britain and in most Arthurian retellings and adaptations. If you'd believe Nennius, he is solely responsible for everything that went wrong in Britain after the Romans left.

And the story goes that Vortigern was fooled by a Saxon leader called Hengist. Hengist offered Vortigern his daughter's hand in marriage, in exchange for the rights to settle in Britain. Besotted, Vortigern agreed, and the Saxons all flooded over at once.

The Anglo-Saxon chronicle puts this later, in 449, and describes the deal as more of a military arrangement. Vortigern sought help from Hengist & his brother Horsa to fight the Picts, and Hengist & Horsa liked Britain so much they decided to invite all of their friends over.

The threat of the Picts (seen here modelling a William Morris print) makes perfect historical sense, because Pictish invasions from Scotland might have grown more common as the legions departed, and 5th C. British leaders might have hired more Saxons to address the problem.

But it probably didn't happen the way it's depicted in the Historia Brittonum. Vortigern is likely a fabrication: it may have been politically useful for later Welsh writers to have someone to blame for the arrival of the Saxons, or perhaps it just made for a better story.

There are plenty of other stories about Vortigern, one of which involves a castle, two dragons, and a young man called Ambrosius. But I think we'll leave that for another time...

430 followers! When I get to 437 I can tweet about the Battle of Wallop.

You know you want to hear about a battle called the Battle of Wallop.

437 followers! Girth your sword and mount your sure steed, because it's time for the Battle of Wallop.

Also known as the Battle of Guoloph, but that's less fun. Traditionally placed near the charming village of Nether Wallop in Hampshire, where Miss Marple was still solving mysteries over a thousand years later. But possibly named because the Saxons got such a good walloping.

437 AD is one of several years in which an important battle between the Britons and the Saxons probably didn’t happen. I’m taking this date from a 1980 translation of Nennius by John Morris, but it could equally have been 458, 440, or never.

Let’s meet today’s challengers! In the blue corner, Vortigern, who you met earlier in this thread. If you remember him from last time then you may not be hugely surprised to learn that a lot of Britons were unhappy with his reign and rebelled against him.