The funeral of Margaret Thatcher is taking place amid tight security on Wednesday, with Queen Elizabeth II leading mourners from 170 countries in bidding farewell to one of Britain's most influential and divisive prime ministers. Seven hundred soldiers, sailors and airmen in full ceremonial uniform will line the streets of London as Thatcher's coffin is transported on a gun carriage to a service at St Paul's Cathedral. Although it is not officially a state funeral, Britain has pulled out all the stops for the "Iron Lady," who transformed the country and helped end the Cold War during her 11 years in power. Some 4,000 police officers have been deployed to the event, amid heightened security following the bombings at the Boston Marathon and fears of disruption by opponents of a politician who still arouses strong passions even in death. Thousands of well-wishers gathered along the route of the funeral procession, which will set off from the Houses of Parliament where Thatcher's coffin lay overnight at about 1000 hrs (0900 hrs GMT). "I just wanted to come and pay my respects to a great lady," said Carolann Henderson, a 57-year-old civil servant from central England who rose at 0400 hrs to secure her spot outside St Paul's. The former police officer said Thatcher had improved her pay and given her the chance to own her home. "I admired Mrs. Thatcher. We worked hard and she gave us the dream." The funeral, nine days after Thatcher died from a stroke aged 87, will be the first time the queen has attended a prime ministerial funeral since Winston Churchill died in 1965. The Falklands War, viewed by many of her admirers as Thatcher's finest hour, will be a central theme of the service with veterans of the 1982 conflict with Argentina walking behind her coffin. Argentina will pointedly not be represented among the 2,300 guests, who include US political figures Dick Cheney and Henry Kissinger, the prime ministers of Canada, Israel, Italy, Poland and Kuwait, and show business stars from Thatcher's time in power. The great and the good of British politics will also attend, led by Prime Minister David Cameron and three former premiers, John Major, Tony Blair and Gordon Brown. All of the current cabinet will attend as well as all surviving members of Thatcher's cabinet, and the opposition Labour leader. But the pomp and splendour -- paid for with millions of pounds of public money -- have sparked criticism from those who argue that Thatcher was too polarising a figure to merit such a state-sponsored send-off. "We're spending £10m ($15.3m) on it and that's disgraceful and unacceptable at a time of austerity," said 22-year-old student Casper Winslow, who held a placard reading "Rest of us in poverty.” Others are planning to turn their backs on the procession in protest at the damage wrought by her radical free-market economic reforms, which created mass unemployment in Britain's industrial heartlands. Cameron defended the ceremonial funeral, during which he will give a reading from the Bible. "I think it'll be quite a sombre event, but it is a fitting tribute to a great prime minister respected around the world," the Conservative prime minister told BBC radio. "And I think other countries in the world would think Britain got it completely wrong if we didn't mark this in a proper way." Thatcher's coffin spent the night at the 13th-century Chapel of St Mary Undercroft in Westminster, after a private ceremony attended by her 59-year-old twin children Mark and Carol and former colleagues. At 1000 hrs the coffin will be dressed with the Union flag and taken by hearse to another church on the Strand, where it will be transferred to a gun carriage drawn by six black horses for a procession down Fleet Street to St Paul's. Members of the military will line the route and a Royal Marines band will lead the way playing funeral marches by Chopin, Beethoven and Mendelssohn. The chimes of parliament's famous Big Ben bell will be silenced during the procession, while guns will be fired from the Tower of London every minute. The coffin will be carried up the west steps of St Paul's by eight men from military units that served in the Falklands, and behind them will walk two brothers who survived an attack on their vessel by Argentina during the war. The service is due to start at 1100 hrs and will include Christian hymns reflecting Thatcher's Methodist upbringing, a Bible reading by her granddaughter Amanda, and a final blessing from the Archbishop of Canterbury, Justin Welby. Britain's first female prime minister, who was in office from 1979 to 1990, had suffered from dementia and was rarely seen in public for the final years of her life. Tributes poured in from around the world highlighting the role she played in bringing down the Iron Curtain by reaching out to reformist Soviet leader Mikhail Gorbachev and persuading US president Ronald Reagan to do the same. Gorbachev and Reagan's wife Nancy will not attend the funeral due to ill-health.