the jewel in someone's/something's crown
the jewel in someone's/something's crownor
the jewel in the crown of someone/something
COMMON If something or someone is the jewel in someone's or something's crown or the jewel in the crown of someone or something, it is the best thing they have, or their greatest achievement. He has written a number of excellent books but this novel is surely the jewel in his crown. The jewel in the architectural crown of North Yorkshire is almost certainly Castle Howard. Note: This expression was known in Victorian times, but is probably most well known as the title of a novel by Paul Scott, published in 1966, that formed part of a series set in the Raj, or Victorian India. In this title, India is seen as the `jewel', and the `crown' is the British Empire.