The Sun – Having won a Golden Globe last year for her plummy-voiced portrayal of the Queen in Netflix TV series The Crown, the 33-year-old British actress appears to be the princess of Tinseltown.
But she is far from royalty.
She was born in Stockport, Greater Manchester, raised by her single mum, worked on the checkout in Tesco for five years and described herself as “a massive commoner”.
Claire’s childhood was marred by illnesses, one of which — a tumour in her eye at the age of 17 — could have shattered her dreams of becoming an actress.
Instead it made her more determined to succeed.
She said: “It was horrible and debilitating, but it made me realise that I needed to grab the life I wanted.
“If that hadn’t happened, I don’t know if I would have been brave enough to throw my cards on the table and say I wanted to study drama.”
Fortunately the tumour was benign and could be treated without invasive and potentially disfiguring surgery.
She said: “I’m quite lucky to have a face. I was a bit like Cyclops and it was all a bit scary.
“I was on steroids for about a year and a half afterwards that makes you put on a lot of weight and have really bad skin.”
Claire grew up in a huge Irish extended family — her maternal grandparents, who came from Dublin and County Kildare, had 22 siblings between them.
Her mum, Caroline, was an office worker, and her dad, David, was a salesman for photocopier giant Rank Xerox.
Claire had an older brother and an older sister, and her parents found paying the bills was already difficult.
But when she was eight they divorced, and her mum became a single working parent.
Claire said: “I don’t know how she did it.
“She took a job that meant she could be there for us when we got back from school. She is an extraordinary mum.
“There is not anything that she has not given us.”
But with money tight, Claire found work in a pub in her teens and said: “I was always very, very aware of money and not having any.
“I always knew there was no money coming from anywhere else, so it was a case of ‘Well, I’ve just got to get out there and make it myself.’”
Pulling pints was just the first of a long line of menial jobs she took in her youth.
She said: “I did telesales, I gave out magazines at Tube stations, I worked at Wimbledon as a security officer. I was a piano teacher for a while, I worked in sales.
“And for a long time I worked at Tesco, which was actually a dream job because I’d always wanted to work on a till.
“Seriously, when I was younger I used to look at tills in the Argos catalogue, I was so obsessed with them.
“So when I started working at Tesco, I was thinking, ‘OK, here we go. Ping! Ping!’ I loved it.”
But Claire’s ultimate job was always going to be as a performer.
Her first ambition was to be a ballet dancer, but soon after the family moved to Longwick in Buckinghamshire, that idea was crushed.
At the age of 13, the previously sporty girl developed juvenile arthritis which left her temporarily crippled and in agony and set her apart from the rest of her schoolgirl pals.
She said: “I was on crutches while the other girls were running around. My knees were swollen while theirs were being shown off in miniskirts.”
The experience gave her confidence a knock.
It was only after the eye tumour at 17 that she applied to study drama at Liverpool John Moores University, and later at the Oxford School of Drama, but it did not automatically transform her into a confident actress.
She said: “I was never the prettiest or the most talented girl. It was always an uphill struggle. I’ve loved drama, but somehow I just thought everyone else was better than me.”
Like most actors, it took her a long time to make her breakthrough, but it came in 2008 when she landed a small part in the pilot of BBC Three drama Being Human, which then saw her get the title role as Amy in BBC1 period drama Little Dorrit, later that year.
After that, the parts steadily rolled in, from the 2010 revival of Upstairs Downstairs, to The Promise in 2011 and Wolf Hall in 2015.
Some of the roles required her to do sex scenes — which Claire hated.
She said: “If I never had to do a sex scene again, that would be the best thing in the world, because no one in their right mind would enjoy that.”
“You’re worried about what the crew are thinking, whether they’re really uncomfortable, whether you’re uncomfortable. You’re just thinking, ‘God, let this be over!’”
While making her first film, 2011 fantasy Season of the Witch, Claire fell in love with co-star Stephen Campbell Moore, and they married in 2014.
The following year she gave birth to their daughter and landed the role of the young Queen Elizabeth in The Crown.
Then at the end of 2016, when the first series aired, Stephen was diagnosed with a benign tumour on his pituitary gland at the base of the brain, which controls metabolism.
The 38-year-old actor said: “You realise you’re not the most important person in that process, and everybody who loves you goes through far worse.
“My daughter didn’t know what was going on at all. But my family did, and I could see it in them.”
The couple, who live in North London, had to prepare for the worst when Stephen had to have more surgery last summer.
He said: “There are certain things that you make sure you’ve done before you go into surgery.
“You write a letter. But it’s all very much on the offchance that something did go wrong, because every part of you is saying that nothing will.
“Waking up and being told the operation had gone well was understandably a huge relief.”
Though Stephen now seems to be on the mend, the fear of losing her husband could not have come at a worse time for Claire.
She could cope with being pregnant while filming the first series of The Crown, but last year she had to make the second series amid the stress of not knowing whether she would soon be a widow.
Now Claire, who has never discussed her husband’s illness, has started a whole new chapter.
After her Golden Globe for The Crown, she has now left the series, with the older Queen Elizabeth being played by Olivia Colman.