14:02 - Here's the schedule for this afternoon:
By 1.15pm: The prime minister, senior ministers, the lord mayor of London, and members of Lady Thatcher's immediate family arrive at the Guildhall from the reception at Mansion House.
2.30pm: The national anthem is played in each room by military musicians and the reception at Guildhall ends.
8pm: Flags raised from half-mast at official buildings.
13:49 - The BBC's political editor Nick Robinson points out the extraordinarily powerful symbolism of the Queen, the monarch, standing on the steps of St Paul's as she watched the body of a politician being taken away.
13:37 - My colleague Henry McDonald has sent this from Derry: Derry's heavily fortified courthouse seems to be the only building today on the overwhelmingly nationalist west bank of the city where the Union flag is flying at half mast. There is a heavy security presence in the city.
13:35 - Nick Robinson Political editor: Again and again the crowd cheered, as if they wanted to say, "after all this contention and debate, we're here to cheer you on your last journey".
13:34 - Two VIP receptions are now taking place. This is what Number 10 said about them in an earlier briefing note.
The Foreign Secretary will host a reception at the Mansion House for representatives from foreign states and other distinguished foreign VIPs. At Guildhall there will be a reception for friends and family of Lady Thatcher and representatives of UK institutions. The Thatcher family, the Prime Minister and other senior Ministers will attend both receptions.
13:32 - Gerry Holt BBC News: It is not only Brits who have turned out today.
Lesley-Ann Coker, 37, from California, says she has never seen anything quite like it. "When the carriage passed by I just kept saying 'Wow'. I got goosebumps and I'm still shaking."
9:35 - Stood outside St Pauls selling "I was there" t-shirts. The sort of entrepreneurial spirit she would have wanted, tweeted Mike Landers.
8:55 - The crowds are really beginning to build now, even as rain begins to fall from the pale white skies above St Paul's, says a BBC reporter.
9:13 - Just did the Today program on Thatcher funeral. Said we should not be spending £10 million on a quasi state funeral, says a UK MP.
9:25 - Peter Barron Editor, the Northern Echo tweets: Important news day with Margaret Thatcher's funeral. Glad the Durham miners have said there will be no celebration 'party'. Right decision.
9:27 - Q: Some people feel giving Thatcher something akin to a state funeral is tampering with the constitution.
Cameron does not accept that. What is happening today is "fitting and right", he says. People overseas would think it extraordinary if Britain did not pay tribute to a great prime minister. They would think Britain had got it completely wrong