Former prime minister Margaret Thatcher is due to leave hospital later on Saturday, her spokeswoman said.

The 82-year-old Thatcher was taken to a south London hospital on Friday for precautionary medical tests.

"She has just been given the all clear," the spokeswoman told Reuters. "She is due to see her consultant one more time and then expects to be released this afternoon. The tests were mainly precautionary."

Thatcher has appeared only rarely in public in recent years after suffering a series of small strokes in 2002 which forced her to cancel her busy public speaking schedule.

As Britain's first and so far only female prime minister, Thatcher was dubbed the "Iron Lady", earning a reputation as one of the most formidable politicians of her era.

She came to power in 1979 and governed for more than 10 years before being ousted by members of her own party. She retired from the House of Commons (lower house) in 1992.