Officers were called by London Ambulance Service (LAS) at 22:50hrs on Saturday, 17 March to a residential property on Kingsway, Enfield, where a 51-year-old woman was found unconscious, suffering from a head injury.
She was taken by LAS to an east London hospital where she remains.
A 36-year-old man was arrested at the scene and taken to a north-London police station. He has since been released under investigation.
Detective Constable Séan Keogh from Edmonton Community Safety Unit, said:
“The victim is currently in hospital in a very serious condition. From our initial enquiries, we know that the victim was in the Picture Palace pub, Lincoln Road, Ponders End, at approximately 19:30hrs and left at about 20:00hrs.
“It’s believed she remained in the area of Ponders End prior to being found at the address later that evening.
“I would encourage anyone who thinks they saw this woman and how she came to receive her injuries, or has information that would assist the investigation, to contact police as soon as possible.”
Anyone with information is asked to contact Edmonton Police on 101; to remain anonymous, call Crimestoppers on 0800 555 111.