On screen as Lady Mary Crawley, she is still mourning the loss of her husband.
But this is the Irish charmer who is giving Downton Abbey star Michelle Dockery plenty to smile about in real life, the Daily Mail can reveal.
The actress has been seeing financial PR John Dineen for several weeks.
She was pictured at the weekend
strolling with the dark-haired 31-year-old and exchanging kisses in the Venice sunshine.
But the way they met might not have garnered approval among the aristocratic Crawley family if it had formed part of the storyline in the ITV1 costume drama.
For the couple were introduced by Allen Leech, who plays chauffeur Tom Branson in Downton.
As well as being a colleague of Miss Dockery, also 31, the Irish actor is a friend of her new love.
Mr Dineen, an Irish-born senior director with FTI Consulting, lives near the actress in Clerkenwell, Central London.
Miss Dockery’s father Michael was born in Dublin.
Of their being introduced by Leech, an associate of Mr Dineen
said yesterday: ‘John is also from Ireland and went to University in both Cork and Dublin before coming to London.
‘He is very private and softly spoken but he has really been taken by Michelle. Allen is an old friend and appears to have played Cupid.
‘Friends have joked that they must have also been drawn together because of their Irish connections.’
Mr Dineen was brought up in Waterfall, near Cork, where his parents Patrick and Marie run a farm.
He achieved a BSc in Food Business and Development at University College in Cork before taking a science masters degree in 2005 at University College, Dublin.
Miss Dockery’s father Michael is a Dublin-born lorry driver who became a surveyor after moving to East London, where he raised Michelle with his wife Lorraine. The actress is the youngest of his three daughters.
Genealogists have reported in the past how her family hail from a long line of Irish peasants and East End labourers.
Miss Dockery returns to our screens later this month as Lady Mary. In the last episode of Downton, shown last Christmas, viewers saw her husband Matthew Crawley, played by Dan Stevens, dying
in a car crash shortly after visiting her and their newborn son George in hospital.
Miss Dockery’s agent last night declined to comment on her relationship with Mr Dineen.
The actress was said to be devastated early last year after she split from American architect Trent Davies. They had been together for more than three years.
She briefly dated Holby City actor Joseph Millson but after the pair split he posted a series of tweets bemoaning the end of their affair.
In one he said: ‘Delete delete delete. Photos, emails, texts. Cleaning out.’ In another, he said: ‘Just wait for someone worth being in a relationship with.’