Robert Hardman discussed his new book, Elizabeth II, on the centenary of the late monarch.
He talked about the Queen's many visits to Northern Ireland and Ireland. Once, she arrived just after a bomb had gone off in Ulster. Her security advisers tried to cancel the trip.
'Well, the bomb's gone off already, hasn't it?' the Queen said. 'So of course I'm going to go.'
Robert also remembered the Queen's visit to America for the bicentenary of independence, 50 years ago, in 1976. As she talked to President Ford at the White House, the band struck up 'That's why the Lady is a Tramp.
'The President was incensed,' said Robert. 'The Queen dined out on it for years.'
