Baroness Thatcher was today granted the honour of a ceremonial funeral at St Paul's Cathedral in the presence of the Queen, Prime Minister David Cameron and dignitaries from all around the world.
A coffin bearing the body of Britain's first female prime minister was carried in military procession through streets lined by thousands of mourners and members of all three armed services.
Although the event was not the state funeral received by Sir Winston Churchill, it was conducted with more pomp and ceremony than any seen in London since the death of the Queen Mother in 2002.
A gun carriage drawn by six black horses carried Lady Thatcher to St Paul's, where a congregation of more than 2,300 guests had gathered to pay their final respects.
Earlier, the longest-serving prime minister of the 20th century left Parliament for the last time as a hearse took her body from the crypt chapel of St Mary Undercroft in the Palace of Westminster to the start of the military procession at St Clement Danes in The Strand.
Lady Thatcher's coffin, draped in the Union flag, bore a large bouquet of white roses with a handwritten note from children Sir Mark and Carol Thatcher reading "Beloved Mother - Always in our Hearts".
Prime Minister David Cameron said the funeral was a "fitting tribute" to a major national figure, and urged the Iron Lady's political opponents to show "respect" during the event.
But protesters joined mourners lining the route of the procession, some of them voicing anger over the reported £10 million cost of the funeral.
Cabinet Office minister Francis Maude, who has led Government preparations for the event, insisted today that the cost would be "much, much less" than this figure, but no official estimate has yet been released.
Mr Cameron accepted that opinions were divided over the legacy of Lady Thatcher, who died last week aged 87.
But he said that Britain's first female prime minister had created a new consensus during her time in power, telling BBC Radio 4's Today programme: "In a way, we are all Thatcherites now.
"She was the first woman prime minister, she served for longer in the job that anyone for 150 years, she achieved some extraordinary things in her life. I think what is happening today is absolutely fitting and right."
At dawn today, Union flags and the national flags of the UK were lowered to half-mast at Government buildings and other locations across the country as a mark of respect. They will remain lowered until dusk.
In a poignant journey down streets lined with mourners, the hearse bore the former prime minister's body past some of the scenes of the triumphs and setbacks of her remarkable career.
As it made its way down Whitehall under overcast skies, it passed the gates of Downing Street - Lady Thatcher's home from 1979, when she arrived as prime minister quoting St Francis of Assisi's "Where there is despair let us bring hope", until her tearful departure after being ejected by her own party in 1990.
Prayers were said at the RAF church of St Clement Danes on The Strand by resident chaplain the Rev David Osborn as the coffin was transferred to a gun carriage of the King's Troop Royal Horse Artillery for the military procession.
The carriage made its way at a pace of 70 steps per minute down The Strand, Temple Bar, Fleet Street and Ludgate Hill to St Paul's. The wheels of the 1.5-ton carriage had been changed from steel to rubber so it runs more quietly on the road.
The Band of Her Majesty's Royal Marines Portsmouth led the procession, striking eight bass drum beats to set the pace and playing funeral marches by Beethoven, Mendelssohn and Chopin.
The route was lined by members of all three services in full ceremonial day dress, officers wearing black armbands, with colours draped and rifle muzzles pointed downwards towards the ground as a mark of respect.
More than 4,000 police officers were on duty to ensure security amid heightened fears of a terror attack sparked by the bombing of the Boston marathon in the US.
As the procession moved forward, a gun salute was fired at one-minute intervals from the Tower of London. Among the three 105mm light guns operated by the Honourable Artillery Company were two used in the Falklands, which were last fired in anger at Goose Green and the final assault on Port Stanley.
As the procession arrived at St Paul's there was warm applause from crowds packing the pavements, along with some booing.
The cortege was met by a guard of honour from the 1st Battalion Welsh Guards at the West Steps of St Paul's, which were lined by members of all three services and 16 Chelsea pensioners. A single half-muffled bell tolled.
The eight pall-bearers who carried the casket into the Cathedral were drawn from Army units, Royal Navy ships and RAF stations with links to the Falklands war, commanded by Major Nick Mott of the Welsh Guards who served in the 1982 conflict.
Lady Thatcher's grandchildren Michael and Amanda walked ahead of the coffin as it entered the cathedral, carrying cushions bearing the insignia of the Order of the Garter and Order of Merit, which were laid on the altar.
The Queen and Duke of Edinburgh headed a glittering list of dignitaries from around the world, former colleagues and showbusiness stars attending the funeral, including Mr Cameron and all members of his Cabinet, as well as more than 30 members of Lady Thatcher's cabinets from 1979 to 1990.
Around 170 countries were represented by dignitaries, including two heads of state, 11 serving prime ministers, members of royal families, foreign ministers and ambassadors.
But there were no serving ministers from either the US or French administrations.
President Barack Obama's official delegation was led by George Shultz and James Baker, who both served as secretaries of state during the Thatcher era, while French president Francois Hollande has sent Elisabeth Guigou, a close adviser to Francois Mitterrand while Lady Thatcher was in office.
Former US vice-president Dick Cheney and ex-secretary of state Henry Kissinger were attending in a personal capacity.
In a mark of continuing tensions over the Falkland Islands, Argentine ambassador Alicia Castro declined an invitation to attend.
At the former prime minister's request, the funeral was being framed by British music, with pieces by UK composers played at the beginning and end of the service.
Lady Thatcher chose the hymn He Who Would Valiant Be, while the Charles Wesley hymn Love Divine, All Loves Excelling will reflect the influence of her Methodist upbringing, and the final hymn will be the patriotic verse I Vow To Thee My Country.
The organ played Psalm 84, set to the music of Johannes Brahms, which is the same piece Lady Thatcher chose to be played at the funeral of her husband Sir Denis Thatcher in 2003.
Mr Cameron and Amanda Thatcher were giving readings from the King James Bible, and Bishop of London Richard Chartres was delivering the address.
At the conclusion of the service, a blessing was due to be given by Archbishop of Canterbury, Justin Welby, before the coffin is borne out of the cathedral and returned to a hearse which will take it to the Royal Hospital Chelsea ahead of a private cremation at Mortlake Crematorium in south west London.