Millions live there, millions more visit each year – but how many really know London?

Find out:

- How New York's famous Central Park came to be modelled on a seventeenth-century London square

- When Primrose Hill almost gained a pyramid even larger than the Great Pyramid of Cheops

- Why about 640 people came to be drowned in the Thames in a single night

- What the royal family might do to escape London if the balloon ever goes up