10 most difficult London riddles

Sadiq Khan is a British politician of the Labour Party serving as Mayor of London since 2016, succeeding Conservative Party mayor Boris Johnson. He is also London's first ethnic minority mayor.

The death toll is traditionally thought to have been small, as only six verified deaths were recorded. This reasoning has recently been challenged on the grounds that the deaths of poor and middle-class people were not recorded.

John Snow was an English physician and a leader in the adoption of anaesthesia and medical hygiene. He is considered one of the fathers of modern epidemiology, in part because of his work in tracing the source of a cholera outbreak in Soho, London, in 1854. His findings inspired fundamental changes in the water and waste systems of London, which led to similar changes in other cities, and a significant improvement in general public health around the world.

Ventilation shafts at various points on the route allowed the engines to expel steam and bring fresh air into the tunnels. These shafts were sometimes hidden behind false facades, like the one in the photo (Leinster Gardens 23). The right-hand property is a fake.

Golden Hind was an English galleon best known for her privateering circumnavigation of the globe between 1577 and 1580, captained by Sir Francis Drake. She was originally known as Pelican, but was renamed by Drake mid-voyage in 1578, in honour of his patron, Sir Christopher Hatton, whose crest was a golden 'hind' (a female red deer).

The 2nd Baron of Rothschild was a keen zoologist. He owned the largest zoological collection ever amassed by a private individual: 2,250,000 butterflies, 300,000 bird skins, 30,000 beetles, as well as thousands of specimens of other animals. He sponsored many explorers and scientists, hence many animal species are today named after him. In his will, he donated the collection to the British Museum. It was the greatest accession which that institution has ever received.

The British Museum was opened to the public on 15 January 1759. The covered central quadrangle is called the Queen Elizabeth II Great Court. It has a tessellated glass roof designed by Buro Happold, covering the entire court and surrounds the original circular British Museum Reading Room in the centre. It is the largest covered square in Europe.

The O2 Arena is a multi-purpose indoor arena in southeast London. It opened in its present form in 2007. It has the second highest seating capacity of any indoor venue in the United Kingdom, behind the Manchester Arena, and took the crown of the world's busiest music arena from New York City's Madison Square Garden in 2008.

The Rosetta Stone was found in 1799 in Egypt. Thanks to its writings in three scripts (hieroglyphic, Demotic and Greek), the Rosetta Stone proved to be the key to deciphering Egyptian hieroglyphs. It has been on public display at the British Museum almost continuously since 1802, and is the most-visited object there.

Kew Gardens is a botanical garden in southwest London that houses the "largest and most diverse botanical and mycological collections in the world". Founded in 1840, from the exotic garden at Kew Park in Middlesex, England, its living collections include more than 30,000 different kinds of plants, while the herbarium, which is one of the largest in the world, has over seven million preserved plant specimens.