And so last night, after what felt like months (precisely 12 in fact), Downton returned to the screen. The twitter-sphere lit up with gasps, comments about who looked good in bowler hats and much friendly 'advice' for the show's writers about current and potential future plot lines.

Downton thrives because it achieves a near-perfect blend of fact and fiction - with real events setting a context for the ups, downs and sideways for the Earls of Grantham. The very first episode of the very first series set the tone, with news solemnly reported of the sinking of the Titanic.

While Downton has been a phenomenon, a smash hit on both sides of the Atlantic, it bears many similarities with medieval and ancient Greek literature: blockbuster epics where the blend of reality and a bit of artistic license made story-lines as explosive, dramatic and gripping as the Sunday night prime-time slot is today.

That is not surprising, as all were intended as Entertainment (with a capital E). In the Byzantine Empire there were even the equivalent of the commissioning editor, the svengali looking for a smash-hit that would liven up dinner and the weekends, and get people gossiping at the water cooler (OK, at the baths).

The Alexiad was written in the 12th Century, for example, after the Empress Eirene asked for a good, racy account of the below and above stairs plots in the palace that would have given Downton a run for its money. Ooh - the servants Borilos and Germanos were planning a take-over from behind the scenes in 1080; who'd have believed it ! She even turned to a new writer to keep it going after the first person she commissioned keeled over and died after working too hard (that, and falling ill while on military campaign).

It's easy to think that people were any more forgiving about the blurred lines between fact and fiction then than they are today: Downton is sheer fantasy, says one commentator, sucking lemons. Look at all the historical errors, roar others, their lists eagerly picked up by newspapers with column inches to fill.

And it's made worse by the fact that it's so hard to pick out all the in-jokes and little references - the cheeky asides to Plutarch and Horace that would have brought chuckles, nods and winks to readers of the Alexiad, and to those who had sections of the text read out as after-dinner Entertainment. Just like references to rogue financiers, credit crunches and wars gone wrong abroad to in Downton, the trick was to make it all seem surprisingly modern and relevant - but about 'the good old days' at the same time.

Eyebrows would have raised at the depiction of some characters as being too good to be true and of others taken down a couple of notches. The people who supported the conspiracy of a certain Nikephoros Diogenes in the 1090s were fools, an 'utterly gormless' lot, convinced they were watching a genius when they saw their man chuck a spear a few feet through the air (Prime Time Saturday night audience watching Ant & Dec, perhaps). The hero of the Alexiad, by contrast, was scrupulously fair, always weighing the evidence carefully when given a choice, and really taking his time before making a considered decision (no idea how long it took him to choose from a menu, but you get the sense he was not the ideal person to grab a quick bite to eat with).

The point of the literature was to amuse and instruct, to give an insight into the past; it was certainly not to give a fact based account of history, reported in tones reminiscent of 19th century newspapers that would send you to sleep and question whether improving national literary levels were really worth the trouble. On the contrary - the more skullduggery, evil villains and heroic acts of selflessness the better.

Take Digenis Akrites, for example, one of the great poems of the medieval world (tragically understudied) and its tales of doomed love, of triumph over adversity, of daring and cliff-hangers that would make Julian Fellowes green with envy. Now THAT's Entertainment. Killing bears with your hands - take that Matthew Crawley (sniff); what's that - a dragon? Boom - gone! Think you can do better, Carson?

Or Homer, with the twisting plot lines, carefully-weaved story that was too neat and predictable for some. Well, of COURSE, Odysseus was going to make it home; what did you expect ??! Would his beloved old dog recognise him after only 20 years away; this is showbusiness, guys, so you do the maths. That Cyclops - did you really think he'd snaffle the hero ? Was that nice Branson going to - oh wait, that's Downton again.

The point is that Entertainment is, well, Entertainment. After my bit to push X-Factor viewing figures clearly worked last week, I'm hoping to have the same effect on Downton Abbey. Julian Fellowes, Anna Komnene and Homer; Lady Mary, Alexios Komnenos and Odysseus. 3,000 years of prime time all linked neatly together. You read it here first, people.

As far as our household is concerned, there are three New Years. One on 1st January (fair enough); another when school goes back in September (yes, OK); and another when the new season of X Factor starts at the end of August.

Thousands upon thousands of hopefuls queue up, drawn by the dreams of making in big and by the drive deep within the heart that makes almost every single one of them assert (usually through tears) that 'I really, really want this more than anything, I really really want it.'

I don't know how many other medieval historians watch X Factor - though a straw poll amongst my peers in Oxford suggests more than you might think (just because you obsess about William of Malmesbury's sources or about new coin finds by the Danube does not mean you're not human, you know!). It should be compulsory watching for anyone interested in the Crusades.

In 1095, Pope Urban gave an electrifying speech at Clermont in Central France, calling for armed men to join an expedition to save the Byzantine Empire which was teetering on the point of collapse (I have written a book about this). As word spread around Europe that something was going to be done to save Constantinople, the most important city in Europe with treasuries filled with Christianity's crown jewels, and better still, then carry on to Jerusalem, young men - and women - clamoured to take part.

Their motivations for doing so were varied, many of them conflicting: it was well-known that the journey east was long, dangerous and expensive. So leaving family behind was a wrench; and it cost a lot; and there was a good chance of not making it back alive.

But think of the rewards in the next life - that was the priests' favourite line. Sure. But also think of the glory, said the vaguer, medieval public school types; think of the financial rewards, thought the sharper ones on the make; think of what fun it will be, friends will have cajoled each other; think of what people will say if you don't go (a few of the sterner fathers would have tried that); and remember, darling, with thousands taking part, it will never be safer (the common sense of the mother, I suspect).

Unscrambling those is not easy, despite the solemn and dry explanations set out most historians of this period, who talk religious conviction, faith and endless variations of similar noble causes. Where's the fun, guys - and where's real life?

What about the peer pressure; where's the one drink too many, of course I'm coming promise that turns into something serious. Where's the showing off to the foxy daughter of the local landowner who's bound to be impressed? Where's the reluctant knight who had other things he was planning to do; or the one whose eyesight just wasn't that great and who didn't fancy it?

They are drawn, just like the Crusaders, by the conviction that the upside outweighs the downside: the shot at glory, riches, fame, eternal life made the risk of embarrassment, humiliation and (social) death worth it. Some are egged on by friends whose blind faith in their talent is touching - especially when it is profoundly misplaced; others are driven by desperation, by their fears and their hope of a better life.

For those who go on to the live shows - woohoo ! - and reach the final stages attain a level of fame claimed by those who returned from the Holy Land after the capture of Jerusalem in 1099. The Crusaders were feted and mobbed as One Direction are today; there were signings, portraits, songs - you name it - when they got home.

The Gary Barlow of the age was Bohemond: men wanted to hang out with him; women wanted to marry him. (I can tell you now, by the way, that our Gary is nothing like that 'Norman dog' as one Byzantine source called him).

Just like X Factor has its share of idiots, so did the Crusade. In the case of the TV show, the worst that happens is that security gets called and a can or two gets kicked by the wannabe hero who comes off the hinges; in the Crusade, there was no such safety net: thousands of Jews were murdered as the lunatic fringe went on the rampage, shouting ever louder how much they want it more than anything. The Y generation in the 11th century gave as little reason to proud as their peers ten centuries later.

This week David Attenborough has spoken of his belief that humans have stopped evolving. I can't tell you much about that. But what I can say is that human beings have not changed so much as some of my medieval historian colleagues think. Just because it was the Middle Ages, not all men were noble, not everyone was convinced by devotion, not all were pious, and not everyone was guided and led by their faith.

That, of course, is what the Simon Cowells of the day wanted you to believe. The medieval monks who wrote the histories of the Crusade and of this period were PR men par excellence. No superyachts, fast cars and messy relationships for them (erm...); but just like with the evil genius behind X Factor, the cash flowed in. All those cathedrals where you went if you wanted to hear real singing weren't free, you know.