An 82-year-old woman is thought to have been beheaded in the garden of a north London house.
Palmira Silva was found at an address in Nightingale Road, Edmonton, at about 13:00 BST, police said.
Officers found her collapsed in a back garden and she was pronounced dead at the scene.
A 25-year-old man was arrested on suspicion of murder and is in custody. Detectives said there is no suggestion the killing had a terrorist motive.
The man is in hospital being treated for injuries suffered when he was arrested, police said.
‘Lives on the line’
A Taser was used during the arrest and a firearms officer is believed to have suffered a broken wrist.