A 54-year-old man was taken to hospital after he was found by emergency services with a serious head injury in Amhurst Park.
Police were called by London Ambulance Service (LAS) to an address on the Hackney street which passes through Stamford Hill and Stoke Newington.
At around 2am, officers found a man injured on the road suffering from a serious head injury.
The 54-year-old was treated at the scene by paramedics before being taken to hospital, where he remains in critical condition.
Enquiries are ongoing into the circumstances.
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