Baroness Thatcher's ceremonial funeral is a "fitting tribute" to a major national figure, David Cameron said.
Mr Cameron told BBC Radio 4's Today programme: "I think it will be quite a sombre event but it is a fitting tribute to a great prime minister, respected around the world.
"I think other countries in the world would think Britain had got it completely wrong if we didn't mark this in a proper way."
The Prime Minister urged the Iron Lady's political opponents to show "respect" during the event, even though they may have disagreed with her policies.
The Queen led mourners at the ceremonial funeral of Baroness Thatcher in St Paul's Cathedral today as thousands lined the streets of London.
Falklands residents say they owe their freedom and their riches to Margaret Thatcher. Today they paused to reflect and to remember.
Baroness Thatcher was honoured with a ceremonial funeral at St Paul's Cathedral in the presence of the Queen and dignitaries.