A £10,000 reward has been offered to catch the attackers of a 98-year-old man left fighting for his life after being robbed in his home.
Peter Gouldstone was found with a head injury and bruising at a house in Evesham Road, north London, on Tuesday.
His son Simon Gouldstone said he "feared the worst" when he found him beaten and in a "semi-conscious state".
The charity Crimestoppers is offering a reward for information to catch those responsible for the "horrific attack".
There was clear evidence of disturbance at the property and a number of Mr Gouldstone's possessions had been taken including a 26-inch Panasonic television, police said.
Det Insp Paul Ridley said: "Mr Gouldstone was left for dead in his own home, a place where he should feel safest.
"There is no way of knowing when he would have been discovered. Had it not been for a member of the public raising the alarm, I believe that Mr Gouldstone would have succumbed to his injuries."
Mr Gouldstone spoke to a family member by phone on 5 November at 14:00 GMT. The attack took place in the 20-hour window between then and when he was found.
He remains in a life-threatening condition at an east London hospital.