Lady Thatcher led Britain from 1979 to 1990
Former Conservative prime minister Margaret Thatcher is under observation in hospital after breaking her arm.
The 83-year-old suffered the injury in a fall at home but is said by her office to be "recovering well".
She had been due to return home after treatment but doctors at the Chelsea and Westminster hospital have decided to keep her in overnight.
Britain's first woman prime minister celebrated the 30th anniversary of her election victory earlier this week.
Lady Thatcher's office said there were no complications or other health issues to be concerned about, following her accident.
"The hospital's decided, just to be sure, to keep her in for observation," her spokeswoman said.
"It's a simple fracture, but bearing in mind who she is, she's 83 and the shock to the system, it's just belt and braces. There is nothing untoward."
They confirmed she had tripped and fallen at about 0800BST. An ambulance was called and she was transferred under police escort, with her special branch protection detail, to the hospital.
She was given an X-ray and it was discovered she had fractured her upper arm.
Lady Thatcher, who led Britain from 1979 to 1990, has become increasingly frail in recent years and has suffered a number of minor strokes. Her daughter Carol has also spoken about her struggle with dementia.
Ill health forced her to abandon her regular public speaking engagements in 2002 but she still makes public appearances.
In March last year she spent the night in hospital after feeling unwell while having dinner with friends.
But earlier this week she was at the Carlton Club in London to mark the 30th anniversary of her historic election victory.
In September 2007 Gordon Brown surprised many of his own backbenchers by inviting the peer to visit Downing Street and praising her as a "conviction politician".