The family of a 90-year-old Second World War veteran who died after being violently robbed in his home have appealed for help to catch his killer.
Geoffrey Bacon was ambushed at the doorstep of the flat in Camberwell, south London, where he had lived for more than 40 years.
The widower suffered a broken hip as his attacker ransacked his Peabody Estate home and escaped with just £40 and his bus pass.
He was left banging the floor of his hallway with his walking stick for half an hour to raise the alarm.
Police said Mr Bacon, who once worked as a driver for United States General Dwight Eisenhower, spent 11 weeks in hospital recovering before dying on August 5.
A post mortem examination found he died as a direct result of the attack almost four months earlier.
Mr Bacon's son, Philip Bacon and daughter-in-law, Jean, both 63, of Whitstable, Kent, said they were shocked anyone could target someone so frail.
Mr Bacon said losing his independence was the "final straw" for his father, a well-known and liked character in the area, who became "disillusioned".
He added: "He was attacked from behind and punched and kicked on the ground. He had bruising to his shoulder and a broken hip. How could anyone do that to a poor old chap?
"They went out and shut the door and just left him there. He hammered on the floor with his walking stick for 30 minutes and called out for help until a neighbour heard and called the police.
"If he had asked my dad he would have given him the money, £30 or £40, whatever he wanted it for. There was no need to attack my dad, no need at all."
Mrs Bacon added: "Why for that small amount of money? And why would you hurt someone so frail? He couldn't understand why someone would do what they did to him."
The attack took place after Mr Bacon visited shops on Butterfly Walk and returned to his flat on Camberwell Green on Monday April 26.
As he entered the flat, he was violently bundled to the floor by a man who punched him in the face and demanded money.
Police are searching for a light-skinned black man, aged between thirty and forty, who may also be responsible for a second attack on the same day.
A 66-year-old woman, walking with a stick, was assaulted and had her handbag stolen by a man who then hit her with it.
Detective Inspector Richard Beadle said a reward of £20,000 was on offer for information that would catch the culprit.
He said: "This is the sort of crime which touches a chord with people, it certainly touches a chord with those investigating it.
"Geoff was the epitome of the London man. He loved Camberwell and suddenly that life long feeling was taken away.
"This was a despicable robbery - we're talking about an extremely vulnerable elderly man attacked from behind.
"It is the worst you can possibly imagine and it has led to the worst possible outcome.
"We have an investigation that's now four months old and has become a murder investigation. We need to progress it further and we are offering a £20,000 reward.
"This attack ultimately killed Geoff Bacon and we will do everything in our power to find the person responsible.
"Someone who carried out a cowardly attack on an elderly man but we are asking anyone who has any information on someone who is attacking and ultimately killing elderly people to come forward."
Mr Bacon joined the Territorial Army in 1937 and was drafted in to the regulars when war broke out.
Initially based in Newbury, Berkshire, he served as a driver in the war before leaving in 1946.
Mr Bacon worked as a vehicle mechanic before joining the Post Office at Mount Pleasant and retiring in 1984.
He had two children, two grandchildren and three great-grandchildren. His wife, Edith, died in 2005.
* Anyone with information is asked to contact the incident room on 0208 721 4961 or Crimestoppers on 0800 111 555.