Long-lost family of a German-Jewish refugee who died alone in his Maida Vale flat will gather on Sunday for the stone-setting.
In December 2010, British Ort was contacted by police searching for relatives of Franz Joseph Nebel, whose body had been found some months earlier.
British Ort executive director Dr Noga Zivan said police had found a reference to Ort at the flat - Mr Nebel had attended an Ort school in Berlin. Although Ort was unable to help the police, it "arranged the funeral for Mr Nebel, which took place on Boxing Day 2010 in the presence of only a British Ort staff member and her husband, as well as one old boy and his wife."
But relatives have since been located and the stone-setting will commemorate Mr Nebel, his two brothers, parents and wife.
"His neighbours, friends and newly-discovered family have been invited, so that we can give him the proper ceremony he deserved," Dr Zivan said.
Among those at the stone-setting will be Israel-based civil engineer Uri Nebel Inbal, a second cousin. "I have done a lot of research into family history and found people living in Brazil, Argentina, Sweden, all over the world. It's quite amazing," he said.
"I have visited England maybe 20 times on business but I never thought to check the phone book to see if I recognised any names."
The Berlin school was set up for German-Jewish children who could not attend mainstream schools in the Hitler era.
It was eventually decided to move the 215 pupils to the UK and a group of 104 boys and seven teachers left three days before the outbreak of war. The second group never made it out of Berlin.