Who is the best-selling writer in history after Shakespeare and the Bible? The answer is Agatha Christie who was born in Devon in 1890 but whose stories often feature London and who wrote what is the capital’s (and the world’s) longest-running play The Mousetrap, which is still playing at Saint Martin’s theatre sixty-five years after it opened. One of the original cast was the late Sir Richard Attenborough, who was paid partly with a share of rights from the play. These were never expected to be worth much but later in his career he was able to sell them to help finance his film about the life of Mahatma Gandhi starring Sir Ben Kingsley.

It's got to be one of London's best-loved events: from the arrival of the eagerly awaited annual catalogue and the feverish planning of visits, to that autumn weekend when the city flings open its doors to citizens and visitors. Yup, it's Open House - time for Londoners to get up close and personal with buildings they normally can't access.