Former British Prime Minister Margaret Thatcher was admitted to hospital Wednesday after feeling faint, and doctors said she was in stable condition and resting.

London's Chelsea and Westminster Hospital said the 80-year-old former leader, who governed Britain from 1979 to 1990, had undergone a number of tests and was being kept in the hospital overnight as a precaution.

British Broadcasting Corp. television reported that Thatcher felt unwell during a hairdresser's appointment and was taken to the hospital by her bodyguard.

"She will be assessed by doctors in the morning. Her condition is stable and comfortable and she is now resting," hospital spokesman Mark Purcell said Wednesday.

Conservative Party spokeswoman Zoe Healy said doctors were confident that she would be well enough to leave Thursday morning.

Thatcher celebrated her 80th birthday at a star studded party in October attended by Queen Elizabeth II and managed a curtsy. But she has grown frail in recent years following a series of small strokes and her public appearances have been rare.

She has given up most public speaking on her doctors' advice, but is still greatly admired, 15 years after leaving office as Britain's first female prime minister.

With her forceful personality, Thatcher dominated British politics throughout the 1980s. Her free market philosophy, push to privatize state industries and hard-nosed battles with labor unions redrew Britain's economic landscape. Even Prime Minister Tony Blair, whose Labour Party languished in opposition while the Thatcher held power for more than a decade, has adopted many of her free market policies.

Her hard-driving style earned her the nickname "Iron Lady," a term reinforced to some in 1982 when she led Britain into war against Argentina after it invaded the Falkland Islands, forcing it to retreat.

Purcell said Thatcher was brought to the hospital's accident and emergency department at 5 p.m. "She has had a number of tests and she will remain in hospital overnight as a precaution," he said.

Thatcher has remained a powerful voice in the party and the Conservatives have struggled to recover from her resignation in 1990, which was prompted by a revolt among her own ministers. But there is a sense that her influence is waning. The appointment Tuesday of youthful modernizer David Cameron, 39, as the party's fifth leader since her resignation heralds a generational shift.

"I was sorry to hear that Lady Thatcher is unwell. I wish her a full and speedy recovery," Cameron said in a statement.

Thatcher was hit hard by the death of her husband Sir Denis in 2003. She also had to endure seeing her son Sir Mark Thatcher arrested in South Africa last year and given a four-year suspended prison sentence after he pleaded guilty to unwittingly helping bankroll a failed coup in Equatorial Guinea.