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

Do you know when Big Ben first bonged – or even who Ben was? Why the River Thames is so-called? Which top Nazi was locked up in the Tower? Or what runs through the more than 50 miles of train-size tunnels which ring the city, stretch further than the Channel Tunnel and lie deeper than the Tube – and, no, the answer's not trains.

The world's first celebrity chef, its oldest club, the worst ever mockney accent, a chapel full of prizefighters and the last Prime Minister to challenge a rival to a duel with pistols - from the truth about Handel's ears to hippos living in Trafalgar Square, it's all in When Did Big Ben First Bong?, the ultimate trivia guide to the greatest city on Earth.