LONDON (REUTERS) - The coffin of former British prime minister Margaret Thatcher was carried into St Paul's Cathedral for her funeral on Wednesday after she had been applauded by thousands of people lining the route.

Her coffin was carried into the cathedral where 2,300 mourners waited, led by Queen Elizabeth II, Prime Minister David Cameron and three of his predecessors and guests from 170 countries.

Lady Thatcher was honoured with a gun salute from the Tower of London every minute and the silencing of Big Ben's bells.

British military musicians played Beethoven, Mendelssohn and Chopin to accompany the grandest funeral for a British politician since that of her hero, Winston Churchill, in 1965.

"She was the first woman prime minister, she served for longer in the job than anyone for 150 years, she achieved some extraordinary things in her life," said Prime Minister David Cameron, leader of Thatcher's Conservative Party.

"What is happening today is absolutely fitting and right,"he said, dismissing concerns by Thatcher critics about the cost and pomp of the event.

Supporters of the most influential British prime minister since Mr Churchill clapped as Mrs Thatcher's coffin, draped in the Union Flag, rolled past first in a hearse and then on a gun carriage along the streets leading from the Palace of Westminster to St Paul's, the cathedral which dominates London's financial district.

A handwritten note placed on a wreath of white flowers on her coffin read: "Beloved mother - always in our hearts".

Mrs Thatcher, who governed Britain from 1979 to 1990, died on April 8 after suffering a stroke.