A woman is thought to have been beheaded in the garden of a north London house.
The victim was found at an address in Nightingale Road, Edmonton, at about 13:00 BST, police said.
In a statement, the Met Police said: "On arrival officers discovered a female collapsed in a garden area."
A man has been detained and is custody. Detectives said there is no suggestion that the killing had any terrorist motive.