Recently I've been watching Downton Abbey. Somehow I'd managed not to catch any as it was broadcast, but a blu-ray boxset received as a Christmas gift finally had me installed in front of the television to see exactly what it was drawing endless tourists to visit Highclere Castle in Wiltshire in a way which television programmes rarely do.

The answer, of course, is that Downton is engaging, character-driven stuff, an Upstairs Downstairs for the 21st century. Indeed, its success prompted Auntie Beeb to attempt the rekindling of that venerable title, with markedly less success.

Part of the formula which makes Downton a success, however, is also the element which - as a writer - I feel weakens it. That is the determination to thread the characters' stories through historical events - as many as possible. The second series, for example, starts at the outbreak of World War I and ends with the Spanish Flu outbreak five years later. Whilst this provides the drama of confining a key character temporarily to a wheelchair and the emotional hook of the woman he felt compelled to marry dying and thus leaving him free - after a suitable period of morbid self-examination - to pursue the woman of his dreams, the rapidity of the historical backdrop leads to some weaknesses in the other story threads. So, for example, one episode ends with the discovery that Bates' spiteful wife has died in mysterious circumstances; the next, set some months later, quickly glosses over this point by having a character mention it in exposition only to confirm it was suicide. By the end of the episode Bates is arrested for murder, but when it finished I half-expected the next episode to commence some months later with his either having been exonerated or being well on the road to it.

Another episode opened with a mysterious war veteran claiming to be the long-lost heir to the family, only for him to have fled the scene forty-five minutes later, presumably because the author knew there was a big time-jump in the offing. A potentially interesting development was thus dispensed with as if it were little more than a tick-box in a historical checklist. This approach robs the programme of dramatic tension both by what they are forced to rush and by what they jump. Imagine if Dallas had followed the Who Shot JR moment with the next episode set after JR was fully recovered and his would be murderer already under arrest - it would rightly be regarded as a damp squib of the same order as when Bobby emerged from the shower and claimed the last few years had been only a dream. The third series of Downton has gone some way to improving this problem, with rather more continuity between episodes, but it seems to have done so by stripping out a great deal of the historical backdrop, leaving only a hint of the situation in Ireland.

So does this mean that you can only manage one or the other - historical or dramatic narrative - and that never the twain shall meet? Other shows have covered longer spans of history. Take, for example, The Tudors. To cover Henry VIII's reign from almost the coronation till his death in a little short of forty episodes clearly required a certain amount of compression, but it handled it without any sudden leaps or hanging plot threads. This is because the history itself is the heart of the story - all extraneous subplots have been subordinated to the history, meaning that the passage of time is sped up and slowed down to suit the narrative arcs chosen. But the Tudors, like the Borgias, has it easy in this regard: most of the characters and story-lines are real, meaning that narrative is served simply by choosing which to focus on at a given point in time.

Indeed, the show which best managed the marriage of fictional narrative and history is Rome. Telling the story first of the rise and fall of Julius Caesar, then of the rise of his adoptive heir Octavian (later Augustus Caesar) was always going to be rich in drama, but the threading through of the stories of Lucius Vorenus and Titus Pullo was what made the show great. Because of the show's early cancellation, Bruno Heller was compelled to accelerate the historical developments in the second season, but it is a testament to the skill of the writer that this was done without feeling disjointed. No episode started with characters expositing about the events unfilmed after the previous.

Rome has, of course, been criticised for not telling history exactly as it was. It wasn't like I Claudius, a dramatisation of history (or, more accurately, a dramatisation of Suetonius' sensationalised rendering of said history). But this wasn't because Heller didn't do his research properly - he made conscious decisions to tweak the history to suit his narrative. Historians may carp here and there, but the show's success spoke for itself and none of the tweaks were contentious outside of academic circles.

But maybe that's Downton's problem. Maybe, with the history being fresher, it is more publicly contentious to play with it. People would be far more likely to complain if you shortened the First World War than if you chopped a couple of months off of the First Punic War - if only because they'd be more likely to realise that's what you'd done. Including a mobile phone in 1924 would invariably lead to complaints from viewers or readers, but including a fork in the thirteenth century wouldn't, despite being every bit as anachronistic. Is the secret to historical drama more about distance?

Speaking as a writer of comic historical fiction, I have to say much of this is academic. When you're writing comedy, you don't have to be entirely a slave to history, as long as you don't make any glaring errors which are clearly not deliberate. So, if I want to replace an English king with a French interloper for the sake of a laugh, I can. If I want to move the Southampton plot's conclusion from Portchester to Conisborough, people won't take it too seriously. If I want Queen Elizabeth to form a rock band on lead electric banjo... well, it's a matter of tone whether that would work (I may come to that in a future article).

The point is that the pliability of history is entirely a matter of context. You can play faster and looser with the things people are unlikely to know than with the things they will have been taught in school; you can have more fun when you're being silly and you can exercise vastly more lassitude when the central characters are definitively fictional. On that basis for now I'll stick to my silly wanderings in ancient history and leave Julian Fellowes to the twentieth century - he seems to be doing fine with it.