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.

London is a port city, and Britain became great because of its navy and ability to trade across the globe. The capital’s wealth is built upon that sea trade. There are reminders of London's maritime history everywhere. In Trafalgar Square, we commemorate the 1805 victory (and the death) of Admiral Lord Nelson at the Battle of Trafalgar. At Tower Hill, we remember the 36,000 merchant mariners lost at sea with no known grave. And the Museum of London Docklands examines the triangular trade in goods, sugar and slaves, upon which so much of the city’s wealth was built.