Chi Hieu Nguyen, 19, started learning English only at the age of 11 at his local high school in Binh Dinh, a town in one of the poorest regions of central Vietnam.
He won the AQA A-level student of the year title after being awarded four A-grades and scoring the best results in the country in his statistics exam, in the summer. Admitting he was shocked to receive the accolade, he said: "Maths is not even my best subject. I am more inclined to history, languages or geography. I cannot believe it."
Chi Hieu excelled at maths and languages at school and at the age of 16, went to one of the country's leading schools in Ho Chi Minh City, before winning a scholarship to study in the UK.
It was Chi Hieu's greatest wish for his parents to see him picking up his award. But they were unable to get visas to fly from Vietnam to see their youngest son at the event, organised by the country's largest exam board.
"When I graduate I'm going to make sure they'll be here," he said.
The couple gave up their low-paid teaching jobs and set up an electrical shop to pay for their three sons to go to the top Vietnamese school. Their sacrifice paid off two years ago, when Chi Hieu won a scholarship to study A-levels in Britain after a representative from Cambridge Tutors in Croydon visited his school.
The private college offers bursaries to students from developing countries.
He came to Croydon, aged 17, knowing little English.
Chi Hieu, who won a gold medal, a cheque for pound;250 and a personal diploma in a ceremony at the Queen Elizabeth II conference centre in central London, said: "I had never even been abroad before I came to England because my family could not afford it."
Chi Hieu is now reading economics at the London School of Economics.
He aims to work for a major international finance body, such as the World Trade Organisation or World Bank, before returning to work in Vietnam.