Police in Barnet are asking for the public to help identify a man who was found collapsed in Regents Park Road, N3 on Friday, 6 July.
Officers were called at around 11:03hrs by London Ambulance Service colleagues after the male was discovered unconscious; he is believed to have fallen over and hit his head.
He did not have any form of identification on him and attempts to identify him have been exhausted.
He remains in hospital in a critical condition and his next of kin have not yet been informed.
The male is described as white, of stocky build, with stubble and a shaved head.
When found he was wearing blue jeans, a black hooded top, and grey Nike canvas shoes.
He was in possession of some change, keys and a small metal necklace.
He has a large scar running vertically from his navel to his chest, believed to be a surgical scar from a possible heart procedure.
The male also has numerous tattoos, including a very distinctive design running up his left arm onto his chest featuring skulls and a face.
Officers are asking anyone who recognises the male to get in touch via 101, quoting reference 2734 of 6 July.