What most viewers will not realise is that the heartwarming storyline about finding love after your youthful dreams of romance have faded will have had great resonance for the actress who plays Mrs Hughes, Phyllis Logan, 59.
For in an extraordinary mirror image of her character's life, Phyllis is virtually a newlywed herself, having tied the knot at the age of 55 for the first time in 2011.
Records kept by Clark County, Nevada, reveal that she married Kevin McNally, a fellow actor, on August 15, 2011 - amid the spectacular surroundings of the Grand Canyon.
As she told an interviewer with an understatement worthy of her Downton alter ego: "There's an excitement in discovering that you can still fall in love when you're an ancient old trout."
Heartbroken by the end of an 11-year relationship that finished when she was 35, Phyllis went on to meet McNally, the man of her dreams, when she was 38. What's more, she went on to bear him a child - a fact which delighted and astonished them both - when she was 40.
"When I found out, I was numb at first," she said. "At my advanced age you don't really think you will have a baby."
Phyllis Logan was born in 1957 in Johnstone, outside Glasgow. Her father was a trade union leader. Although there was no showbusiness in her family history, she set herself calmly onto that path as 'an interesting alternative to working in a bank' and one which would allow her to travel beyond Paisley.
She went to the Royal Scottish Academy of Music and Drama in Glasgow at the same time as Ruby Wax, Sheena Easton and Gregor Fisher, later famous as TV's Rab C. Nesbitt. She worked at Dundee Repertory and appeared in several TV series, including Inspector Morse and Another Time Another Place.
Her big television break came when she played the upper crust Lady Jane Felsham in Lovejoy - a role she occupied for seven years. Her will-they-won't-they romance with roguish antiques dealer Lovejoy, played by Ian McShane, never did reach a happy ending and she left in 1993, feeling the drama had passed its peak.
By this time she had moved to Finchley, North London, and had recently broken up with Paul Pender, a screenwriter. She said that she hadn't wanted children when she was with him, and the romance ended when he went to live in Scotland.
Although she had vowed never to date an actor, saying that they were "too vain" for her, she met Kevin McNally on the set of a drama, Love And Reason, in 1992.
At the time, RADA-trained Kevin was in a romance with actress Stevie Harris, and they had two young children together, Peter 12, and Rachel, six. And with his booming voice and laddish sex appeal, he seemed an odd partner for shy, softly spoken Phyllis. They bumped into each other again two years later, when Kevin and Stevie had broken up. He said: "I'd seen her occasionally but she was just another old luv, really."
He added: "I was the worse for wear that night, but Phyllis indulged me by letting me pour out my troubles. I was knocked out by her right away. She's amazing, so sane, calm and thoughtful."
That was in 1994. Two years later, they had a baby, David. Phyllis said: "I'd never had maternal passions. I sometimes thought I was hardly capable of looking after myself, let alone a child. When you have 20 years of your adult life to get used to not having dependants, it's daunting."
She added: "Not everybody is in the lucky situation where they've met their life partner at 30. I don't think 40 is unreasonable. My cut-off point would be 45 - then you're having a pension while they're still at school. You don't want to be a fuddy-duddy."
She told another interviewer motherhood at a late stage was a wonderful surprise. "We'd discussed having a child, but Kevin managed to wheedle out of making the decision. 'It's up to you,' he said. A typical man. So we left it in the lap of the gods.
"I thought I was probably infertile. Then a close friend looked at me one day and said, 'You're pregnant'.
"I told her not to be so stupid, but she was so certain that she bought me a pregnancy test. I was gobsmacked when it came out positive."
WheN the news was relayed to Kevin, who was in the West End, she says: "He was ecstatic. So much so that for days afterwards he kept missing his cues on stage. I was the one who had the doubts.
"I remember we were in bed one night, reading our books before going to sleep, and I said to him: 'Do you think we are doing the right thing?' Kevin glanced up from his book for a second and said: 'Our child is going to give meaning and relevance to the rest of our lives together.'
"I was gone. I burst into tears. It was the loveliest sentence I've ever heard." He was present for the birth of David, now 19 and at university, and told Phyllis: "Darling, I can see our little baby, it's a beautiful boy."
Phyllis continued to work - playing opposite Helen Baxendale in the TV series An Unsuitable Job For A Woman. McNally was then cast as Joshamee Gibbs in the first of the Pirates Of The Caribbean films.
She was in the habit of travelling to visit him on set with David.
"When Kevin does Pirates, I usually go with him. We've been to the Bahamas and Hawaii. David and I have had some lovely holidays and when he was younger the make-up teams dressed him as a pirate and covered him in scars."
They have busy careers but try not to be separated for more than eight weeks at a time. They phone, text and Skype every day when apart.
"When Kevin's not around, I do miss talking to him. We're such good mates and I tell him more than I tell anyone. We're quite different, though - he's more tidy than me," she said.
In 2011, McNally joined Downton - as the dour grandfather of housemaid Ethel Parks' baby, born out of wedlock - which allowed them to work together for only the second time in their careers.
"When Kevin said he'd got a part in Downton, I thought he was winding me up," she said. "I kept asking him, 'No, what are you really doing?' When I realised it was true, I was a bit miffed that he hadn't asked me first, but I liked having him around and I'd love to work with him again."
After filming, they took a holiday in California and finally got married - eight years after he proposed. The foreign wedding, she says, was 'Kevin's wild and wacky idea but it was fabulous. Hot as hell.
"I never thought real love - the sort where your blood tingles and your world explodes with joy - would happen to me at my time of life. I believed I had missed out on it. But I'm ever so glad it happened."
- Daily Mail
