Factual error: There's more PIR's (movement detectors used in security systems) in Hireclere than you could find in a security warehouse! Just look behind the actors in the corners of a room about 8 feet up. White plastic things about the size of a packet of smokes. I think the earliest units on the market started appearing around the early 70's. The PIR's in Downton Abby look to be around the late 80's onward - pretty advanced for 1914.
Continuity mistake: In several episodes of the early seasons, Carson is said to have once been part of a music hall song-and-dance team with Charlie Grigg, who comes to Downton to blackmail Carson. But in later seasons, Carson is said to have come to Downton at a young age, serving as a hall boy.
Continuity mistake: Every letter's handwriting looks the same - no matter who wrote it.
Character mistake: At one point they say the gramophone was gift for Sybil's wedding. Later they say don't play the gramophone from Mary's wedding, it will make Edith sad.
Episode #1.1 - S1-E1
Other mistake: Lord Grantham tells Violet that he wanted to put 'lights' in the bedrooms but Cora did not, but at the end of the episode just before he blows out his candle Cora turns and off camera turns off a light that "clicks."
Episode #1.1 - S1-E1
Continuity mistake: Near the end of the first episode, when Robert Crawley gets into bed he first puts his candlestick down on the nightstand. Then it disappears. Then when he's in bed and ready to blow out the candle, it's suddenly back again.
Episode #1.2 - S1-E2
Continuity mistake: When Cora (Lady Grantham) goes to Violet (the Dowager Countess)'s house to discuss Matthew and Isobel Crawley, she sits at the table and takes off her gloves shown in a shot from the front, and then the shot changes to over her shoulder and she is seen taking the same glove off again. (00:37:25)
Episode #1.3 - S1-E3
Factual error: The Turkish character "Kemal Pamuk" is given the surname "Pamuk." However, surnames weren't used in Turkey till mid-thirties. Yes, Pamuk is a real Turkish surname but no Turk would be using surnames in 1912.
Episode #1.4 - S1-E4
Factual error: William plays a bit of music on the piano - the tune is called "After You've Gone", and it was written in 1918. This episode is set in 1913.
Episode #1.7 - S1-E7
Continuity mistake: Near the end of the episode with the garden party, there is a scene where Edith is pleading with Anthony Strallan not to leave. You can see Lady Grantham lying down on a lounge chair in the background, with a man who is distinctively Lord Grantham standing next to her talking to her. But the scene immediately cuts to Lady Grantham, her maid O'Brien walks over and Robert is nowhere to be seen.
Episode #2.4 - S2-E4
Continuity mistake: Mary has written a letter to Matthew. We hear her voice reading the text, which begins: "So there we have it. I look forward to introducing the two of you, just as soon as you are next at home..." Next, when the page of the letter is shown, it reads "...happy to hear - come to pass. I look forward to introducing you to Sir Richard, just as soon as you are next at home." (00:11:03)
Episode #2.7 - S2-E7
Other mistake: When the dowager visits Matthew in his bedroom to tell him Mary is still in love with him before he goes through with marrying Lavinia, the curtains hanging behind Matthew are so wrinkled and creased just as curtains are when they come out of a package from the store. The crease lines are terrible! One would think set design would have steamed them as in real life, they would have been custom-made and certainly not folded up like that for shipping, thus never having creases like that.
Episode #3.3 - S3-E3
Other mistake: At the end of this episode after Edith is jilted at the altar, Albert makes some rather "home boy" comments about the food and then asks if there is any cheese to eat as if that's all he's used to or wants. This seems inconsistent since for the rest of the series Albert is the guy who seems to appreciate well-made food and wants to be a cook.
Episode #3.6 - S3-E6
Factual error: Thomas Barrow lights a cigarette with a disposable lighter which were not invented until the early 60's.
Christmas Special 2012 - S3-E9
Continuity mistake: In this episode, Cora tells Mr. Gregson that she started reading "The Sketch" when Edith began to write for him. In Season one, episode one, Carson tells William to iron "The Sketch", because "her ladyship only ever reads the Sketch."
Episode #4.1 - S4-E1
Other mistake: They act as if Carson's friend Charlie has his first appearance in season 4 episode 1, but in an earlier season and episode he arrived at Downton Abbey and caused a scene in the library trying to extort money.
Episode #4.4 - S4-E4
Character mistake: When everyone is preparing to go in to dinner, Robert is wearing an adjustable bow tie. It's bad enough he's wearing black tie to dinner when he has guests, as his mother points out, but Robert, the Earl of Grantham, absolutely would not be seen wearing an adjustable tie with a stand up shirt collar, even among only his immediate family. (00:35:15)
Episode #4.5 - S4-E5
Factual error: When Lady Edith visits a Harley Street doctor his nameplate is shown outside his surgery. His name is prefixed with "Dr." However, one of his post-nominal qualifications is "FRCS." As a Fellow of the Royal College of Surgeons, his name should be prefixed with "Mr.", as with all qualified surgeons in the British Isles.
Episode #4.7 - S4-E7
Factual error: When Edith goes to have an abortion, you can hear a Eurasian Collared Dove singing, but that species did not exist in Britain before the 1970s.
Factual error: Marigold can not possibly be as big as she is in this season. She's bigger than George, when she would only be a few months old.
Answer: Lord Sinderby purchased the house, furnished and appointed, from someone else, complete with staff that come with the home (some of whom aren't happy to be working for a Jewish family). He bought the title, as well. If the artwork featuring Jesus is valuable, he might keep it. Also interesting, his ancestors Anglicized their name, though he is proudly Jewish.
Michael Albert