Former chief policy adviser to Margaret Thatcher, John Redwood, described her as "the best boss I ever had".
"We had to work very long hours to keep up with her," he said.
Fighting back tears he said:
The most moving moment inside the cathedral was when they opened up the great doors and we could hear the noise outside.
It was exactly the kind of tribute you would hope for - we are grieving a loss but also commemorating a life well-led, an extraordinarily active life.
Asked about protests, he simply said: "It is a free country."