Looking "sombre and depressed", according to an observer, Sifiso Masango was the last passenger to board a British Airways jumbo, flight BA057 for Johannesburg.
Twenty-four hours earlier he had become very distressed when about to leave and his departure had been postponed.
Last night the Heathrow airport authorities took precautions against a repeat.
Sifiso was driven onto the tarmac at Terminal Four in a British Airways limousine, with a police panda car acting as escort.
He sat in the back of the car with his mother until all 300 other passengers had got on, then boarded the plane himself, with two plain clothes police officers by his side, a mere four minutes before its scheduled departure time of 9pm. Wearing a black anorak, black jeans and trainers, he stared straight ahead.
His mother looked emotionless as she boarded the aircraft, which finally took off at 9.21pm.
However, his foster mother, Salome Stopford, who had gone to the airport with her daughters Natalie and Simone, wept uncontrollably in the departure lounge. She said : "I just hope and pray that he's all right and that they look after him."
It was the end of a long legal dispute between Mrs Stopford, who is white, and Sifiso's natural mother, who at one time had worked as Mrs Stopford's maid in her South African home.
Mrs Stopford, aged 50, had brought Sifiso up in her family and brought him to Britain four years ago when she moved here with her daughters after the death of her husband.
He has lived as one of the family in Maida Vale, west London, since then and now calls Mrs Stopford "Mummy", speaking English as his first language. He attended school nearby, recently won a scholarship to a British public school and has said he does not want to live in the Transvaal.
However, in March the Court of Appeal ruled that he should be returned to live with his natural parents, and on Friday Lords Justices Neill and Ward rejected a direct request from the President of the European Commission on Human Rights for his departure to be delayed while the commission considered his case.
Sifiso's natural parents have opposed an adoption application from Mrs Stopford since winning the financial backing of a black-rights group and a South African magazine. They claim they expected their son to be sent home to them after being educated in England.
Legal restrictions meant that neither Sifiso nor his foster mother Mrs Stopford could be named until Sifiso left the United Kingdom.