A man was reunited with the father he thought he had cremated after he saw him on television.
John Renehan was amazed to see him on a missing persons appeal programme five years after a coroner formally identified his body at an inquest.
It emerged that John Delaney, 71, was actually alive and had been living in a care home in Oldham, Greater Manchester, since 2000.
He was found in the street suffering from amnesia and was unable to reveal his identity. Mr Delaney was then given the name David Harrison by Oldham Social Services.
Mr Renehan, 42, of Didsbury, responded to the broadcast appeal earlier this year for anyone who recognised "David Harrison" to come forward.
The pair were reunited two weeks ago after DNA tests confirmed they were indeed father and son.
Greater Manchester Police has launched an inquiry to establish the true identity of the man who was cremated in 2003.
The mix-up happened after the discovery of a badly decomposed body in the grounds of Manchester Royal Infirmary on January 10, 2003.
The body was found to match the description of Mr Delaney, who was reported missing from the Mary and Joseph Hostel in Ancoats in April 2000.
Injuries detected were similar to those suffered historically by Mr Delaney and the clothing of the body was similar to what he was wearing when he disappeared, police said.
There were no suspicious circumstances and the matter was passed to the coroner. An inquest was held where the body was formally identified as Mr Delaney and an open verdict was recorded.
Meanwhile, the real Mr Delaney was continuing to suffer from amnesia as a result of a brain injury.
He was transferred to a residential home following his admittance to Royal Oldham Hospital on May 6, 2000, in a confused state.
Social Services were unable to appeal for information until a change in law this year allowed them to do so without Mr Delaney's consent.
Mr Renehan has demanded an apology from police for not running DNA checks on the body but such tests were not widely used to identify decomposed bodies at the time.
A police spokesman said: "Greater Manchester Police accepts that in 2000, the man who was admitted to Royal Oldham Hospital should have been identified as Mr John Delaney and that the inquiries made at the time to establish the unknown man's identity were not sufficient.
"At that time, only paper records of people reported missing from home existed. Today, Greater Manchester Police has advanced systems in place to ensure that mistakes of this nature are not made and robust checks are made to establish the identity of people who cannot immediately confirm who they are.
"Greater Manchester Police accepts that mistakes were made and that Mr Delaney's family has been through a traumatic ordeal. Once Mr Renehan came forward, GMP made every effort to establish the exact circumstances and this investigation has reunited a father and son. The Force will continue to work closely with the family."
GMP added that the officer who dealt with the case in 2000 has since retired.
Mr Renehan claimed his father's memory is slowly starting to improve as he bids to retrace his history.Reuse content