Kate: Where did it go wrong?
The 25-year-old actress, who was tearful and fighting to keep a check on her emotions, spoke of the shock decision today saying: "This is an absolutely amicable separation and it is a mutual decision between both of us.
"Jim and I have great respect for each other. There is no malice at all. It is extremely sad but we are all fine."
Our relationships expert Zelda West-Meads analyses where the marriage went wrong and moon expert Lori Reid reveals why the relationship may have been ill-fated. And we've got a picture gallery charting the love affair that everyone thought would last. Click on the links in the box (right).
Miss Winslet, who will be 26 next month, emerged from the north London flat where she is staying this morning to talk to journalists.
She was wearing a green tee-shirt, blue denim jacket, black trousers and flip-flops, but there was no ring on her wedding finger.
The couple, who have an 11-month baby daughter Mia, remained in touch, she said. They married in November 1998.
The actress told reporters: "Jim and I are both communicating constantly. Mia remains the happy child that she always has been."
Then she added: "That is all and I would be grateful now if you would respect our privacy."
The actress, who was wearing barely any make-up, then disappeared back inside the flat where she is staying with Mia.
Threapleton's grandfather, Norman Threapleton, said the couple may have split because Jim was unhappy living in Kate's shadow.
"Kate made all the running really, she was the one who said she fell head over heels and he made her laugh, and that amused us a little bit because he's a bit serious minded is James," Mr Threapleton told Channel 5 News.
"He's not shy exactly but he just keeps in the background and I think that might have had some effect on him in the months since the wedding.
"He wants to be recognised eventually in his own right and not to be just Kate's husband."
Neighbours said Miss Winslet had been staying for some time in the flat in Islington where she used to live.
The actress is believed to have left the couple's riverside home in Walton-on-Thames, Surrey, several weeks ago. It is believed that the split came after weeks of arguments between the couple.
Miss Winslet's spokesman Robert Garlock said: "No other parties are involved in this amicable and respectful separation. Their daughter Mia will remain first priority for both of them."
Musician David Hancock, 31, who lives in the flat below hers said he had heard a couple arguing there last night and earlier this morning but could not say who it was.
Last night's announcement shocked the showbusiness world, which widely regarded Winslet's marriage as happy and stable.
In a recent interview conducted before the marriage hit the rocks, Winslet said: "Before I met Jim I was very much, you know, 'I don't believe in marriage', but now we just want to be with each other.
"We're totally equal in our relationship, but in certain situations when we go out he wears the trousers," she added.
They married in November 1998 in a deliberately down-to-earth ceremony at the Winslet family's local church, All Saints, in Reading, Berks.
The reception at a pub featured bangers and mash for the guests, who included actress Emma Thompson.
Winslet, who won plaudits for losing so much weight after the birth of her daughter, is due to meet the Prince of Wales later this month at the premiere of her new wartime film Enigma, produced by Rolling Stone Mick Jagger.
Miss Winslet later left her north London flat carrying baby Mia in her arms.
She put her 11-month-old daughter into the baby seat of a blue 4x4 vehicle parked outside the terraced house.
A security guard accompanied her, carrying a pram while her assistant and another woman helped her through a crowd of waiting media.
Miss Winslet then climbed into the back seat of the vehicle and kissed her baby on the head as she was driven away.
The child, wearing blue trousers, a white top and blue socks looked contented as she chewed on a biscuit.
After she left a neighbour emerged from her house and said she had known the actress for around five years.
Martha Brown, 60, who lives two doors away from Miss Winslet's flat, said she thought the star was "just an ordinary girl".
She said: "She is just an ordinary girl to me.
"I think she really loves him.
"It is a temporary bust-up between a married couple. They will get back together."
Ms Brown said she had not heard any arguments from the pair, who she believed moved back to the flat in north London together six weeks ago after their home in Surrey was flooded.
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