1. Downton Abbey is a quality period drama
There have been corsets. Some characters have titles. And occasionally they remember to speak in a manner correct to the period.
But Downton Abbey is not a quality period drama: it's a soap opera that happens to be set in the past. Nothing wrong with that. In fact, it's what many people want on a Sunday night. Let's just not pretend otherwise. Trouble is, the benchmark was set high in the early 1980s, with Granada's Brideshead Revisited, still the most expensive TV series ever made. Quality period dramas are occasionally still made, as viewers of BBC2's ongoing adaptation of Parade's End will agree. But Downton is in a different league: second division, occasionally dipping to third. Still, the last series attracted 10 million viewers and it has saved ITV's fortunes.
2. It's got good characters
There are certainly plenty of them. According to Imdb, there are 54 named parts, so it helps to keep a whiteboard and multicoloured pens handy. The story centres on the Crawley family – the Earl of Grantham, his American wife, and their three daughters – and their struggle to secure the succession of the family home, Downton Abbey. Then there are servants, suitors, cousins and rivals, and plenty of cameo parts. Happily, the script is a bit like The Archers, so they keep telling you who they are and why they're doing whatever it is they're doing. Trouble is, there are so many parts and not enough time to develop them, that we have to make do with pantomime-style goodies and baddies. This season's painted dame is Shirley MacLaine (main), who appears as Lady Cora's mom over from the States. Expect fireworks!
3. It's got good stories
It all started well enough. Three daughters, no male heir, what's a squire to do? The first series was cleverly anchored in history, with the Earl's cousin and son having gone down aboard the Titanic. So when handsome cousin Matthew, played by Dan Stevens, turns up to marry Mary Crawley, a slow-burn love affair begins. Yes, a Turkish visitor died mid-coitus with Lady Mary. And yes, Carson the valet's dark past made him seem more interesting than his single expression would suggest. But it wasn't until series two that Downton jumped the shark, and the plotlines ricocheted off into la-la land. Matthew comes back from the trenches paralysed from the waist down. A few episodes later – he's better! A Canadian officer is nursed back to health in the Downton war hospital. He turns out to be an heir! And then disappears without trace. Downton is commonly praised for being undemanding comfort-telly. On the downside, it requires a jolly big effort to keep our disbelief suspended.
4. Downton Abbey unravels Britain's complex class system
Up to a point, Lord Copper. Yes, it's as much about life below stairs as it is above. And yes, we see the disintegration of Britain's rigid class structure as the First World War takes its toll. But does a clear message emerge? Certainly not for the Americans, who love it, even if they admit to not understanding it. The New York Times says part of its appeal is "that it's so ideologically confusing", and Ann and Mitt Romney say they are fans, even though they don't get it. Over here, it took quite a leap of imagination for some snobs to believe Hugh Bonneville was an Earl. But more to the point: is Julian Fellowes a bit misty-eyed about this lost world of cap-doffing and white tie? Or are we meant to cheer the breaking down of class barriers, as when Lady Sybil drives a car? Maybe life would be better if we all had a Mrs Patmore in our lives, endlessly baking us cakes. Just not for the Mrs Patmores.
5. We care about the love interests
Matthew Crawley and Lady Mary – what a carry on! Will they, won't they? To and fro our emotions go. Or at least, they're supposed to. But these characters are as warm as yesterday's porridge. We know it's a marriage of convenience, but we wonder if they really love each other. Both have had outside interests: she with Kemal Pamuk, the Turkish diplomat who unfortunately croaked in her bed, then getting engaged to Sir Richard Carlisle, the newspaper magnate. Matthew too has been engaged, to Lavinia. Last year's Christmas special ended with them engaged, so expect wedding bells.
6. The language is authentic
Pedants and language historians (is that a tautology?) have had a merry old time pointing out the use of modern phrases. So, when Ethel says "I'm just sayin'" in 1916, she is pre-empting an expression that isn't known to have existed until, ooh, about 40 years later; while "get knotted" is very 1963. Perhaps most bizarre was Matthew Crawley saying: "You've been taking those logic pills again." He might as well have said: "Take a chill pill." But maybe the pedants are the ones who should chillax – this is entertainment, after all.
7. The sets are historically accurate
A parlour game emerged during series one, of spot the howler: five points for a TV aerial, 10 for a plastic conservatory, and 15 for spotting double yellow lines on the roads. The errors occurred during filming on location in Bampton, Oxfordshire, which doubled up as the fictional Yorkshire village of Downton. In fact, much of the period detail that TV producers commonly get wrong was correct, such as the period of cars, or particular clothes fashions. Series two was asking for trouble with its First World War uniforms: internet colonels got into a lather about buttons and regimental attire, and nobody could quite understand why Earl Grantham insisted on wearing a pistol around the house. It's not as if Yorkshire was ever under threat.
8. It's an original drama
Entertaining though they were, some of the plotlines have seemed somewhat familiar. One viewer said she had been left "slack-jawed" by an episode in the first series, which bore a striking resemblance to the 1942 film Mrs Miniver. Another saw parallels with Little Women, saying it was "the finest example of coincidence I have ever seen". Julian Fellowes responded by saying: "Who can say what is lodged in one's brain?" In series two, some wondered whether The Return of Martin Guerre might have become dislodged from Julian Fellowes's brain while he was writing the scene featuring the Canadian heir nursed to health at Downton. The trailer for series three suggests characters are getting in touch with their feelings, as there's plenty of weeping and sobbing. Mr Bates is spared the death sentence for killing his wife, but is sent to jail. And arch stand-offs between Maggie Smith and Shirley Maclaine abound. Who can say what might have been going on in Julian's brain?
9. Everyone's out to get Julian Fellowes
Poor old Fellowes complained of a "permanent negative slant" against Downton Abbey, after the nitpicking began during the first series. In fact, he has become one of the most sought-after scriptwriters around. ITV commissioned him to write a four-part miniseries about the Titanic earlier this year, and he has written screenplays for a film of Romeo and Juliet, and Crooked House, an adaptation of an Agatha Christie novel. He is big in America, and lives in Georgian splendour in a mini Downton of his own in Dorset, with his wife Emma Kitchener (inset right), son Peregrine, and beloved dachshunds.
10. Julian Fellowes was ennobled for services to television
He wasn't: he happened to be ennobled as a Tory peer in January 2011, after Downton Abbey began, but it was for services to politics, not telly. He spent much of his earlier career fundraising for the Conservative Party. Still, it's somehow fitting that Downton should be penned by a man in ermine: if the show has taught us anything at all, it's that Britain's arcane and unfathomable class system isn't going anywhere yet.