Witness

In 1970 the American scientist, Norman Borlaug, was awarded the Nobel Peace Prize for his pioneering work developing disease-resistant crops. At the time famine and malnutrition were claiming millions of lives across the world, particularly in South Asia. Dr Borlaug’s work meant countries like India were able to become self-sufficient. Critics said the new grain varieties were too reliant on chemical fertilizers, but it’s thought millions of lives were saved. Rebecca Kesby has been speaking to Professor Ronnie Coffman, student and friend of Norman Borlaug.(Photo: Dr Norman Borlaug in a field of wheat. Credit CIMMYT International Maize and Wheat Improvement Centre)

By the 1980s a deadly cocktail of factory fumes and car exhausts had turned Mexico City into the world's most polluted city. Hundreds of thousands of people were falling ill each month, many of them children. The Mexican authorities came up with an ambitious plan to curb the use of each of the city's two million cars for one day a week. The scheme was an immediate success and has been copied in other major cities around the world. Ramon Ojeda Mestre, the environmentalist behind the Mexican initiative spoke to Mike Lanchin about overcoming fierce opposition to the plan.Photo: Cars driving through Mexico City. Credit: Alamy

How a young American scientist began the work that would show how our climate is changing. His name was Charles Keeling and he meticulously recorded levels of CO2 in the atmosphere. His wife Louise and son Ralph spoke to Louise Hidalgo about him in 2013. (Photo: Thick black smoke blowing out of an industrial chimney. Credit: John Giles/PA)

The US first began sending troops to the UK in 1942 to help in the war effort. It is estimated that at least two million American servicemen passed through the UK during World War Two and tens of thousands of them were black. The African-American GIs stationed in Britain were forced by the American military to abide by the racial segregation laws that applied in the deep south of the US. But that didn't stop relationships developing between British women and the black soldiers, some of whom went on to have children. Babs Gibson-Ward was one those children. She has been speaking to Farhana Haider about the stigma of growing up as mixed raced child in post-war Britain.(Photo: Hoinicote House children, c.1948. Boys and girls whose parents of mixed ancestry met during WWII. Credit: Lesley York)

In 1963 a small group of British black activists started a pioneering protest against racism within the local bus company in Bristol. It had specified that it did not want to employ black bus drivers. Inspired by the example of the US Civil Rights Movement the boycott ended in victory and led to the passage of Britain's first anti-discrimination laws.Paul Stephenson and Roy Hackett spoke to Louise Hidalgo in 2013 about their part in the protest.Photo: Park Street in Bristol in the early 1960s. (Credit: Fox Photos/Getty Images)

In August 1958 Britain was shocked by nearly a week of race riots in the west London district of Notting Hill. The clashes between West Indian immigrants and aggressive white youths known as Teddy Boys led to the first race relations campaigns and the creation of the famous Notting Hill Carnival. Using voices from the BBC archives Simon Watts tells the story.Photo: Street scene in Notting Hill at the time the race riots broke out in 1958. Credit: Getty Images.

In 1987 Diane Abbott became the first black woman elected to the British Parliament. The daughter of first generation immigrants she was one of only four black MPs elected that day. In 2015 Diane Abbott spoke to Farhana Haider about her journey into the political history books.Photo: Diane Abbott in 1986. Copyright: BBC

The great West Indian cricketer, lawyer and member of the House of Lords took a London hotel to court when it refused to let him and his family stay there in 1943. Susan Hulme brings us his story from the BBC archives.Photo: Sir Learie Constantine outside Westminster Abbey in 1966. Credit: Douglas Miller/Keystone/Getty Images.

In May 1980 China allowed capitalist activity for the first time since the Communist Revolution, in four designated cities known as the Special Economic Zones. The most successful was Shenzhen, which grew from a mainly rural area specialising in pigs and lychees to one of China's biggest cities. In 2017 Lucy Burns spoke to Yong Ya, a musician who has lived in Shenzhen since the 1980s, and to ethnographer Mary Ann O'Donnell.IMAGE: Pedestrians and cars stream by a giant poster of Chinese patriarch Deng Xiaoping in Shenzhen, the first of China's special economic zones. TOMMY CHENG/AFP/Getty Images

Throughout much of 1967 striking workers and students filled the streets of Hong Kong. They were inspired by the Cultural Revolution in China and demanded an end to colonial British rule. Jasper Tsang Yok-sing was then an idealistic young student and he spoke to Rebecca Kesby in 2014.(Photo: Left wing workers put up anti-British posters in Hong Kong outside Government House. Credit: Central Press/Getty Images)

In 1966 Chairman Mao declared the start of the Cultural Revolution in Communist China, a radical and brutal attempt to reshape Chinese society. Saul Yeung was 20 years old at the time and in 2016 he spoke to Lucy Burns about his decision to join the Red Guards, tasked with carrying out Mao's revolution.Photo: Chinese Red Guards reading from Chairman Mao's Little Red Book (Getty Images)

American Sidney Rittenberg first met Mao Zedong in the 1940s during the final years of China's civil war and before Mao's victory over the Nationalist forces. Already a committed socialist, Rittenberg had been stationed in China during WW2 but decided to stay on and fight alongside Mao's Communists. In 2013 he spoke to Rebecca Kesby about his memories of one of the world's great revolutionaries.Photo: a poster of Chairman Mao in Beijing in the 1960s. Credit: AFP.

On 1 October 1949 Chairman Mao declared China to be a communist state. Zhu Zhende was a young recruit in the People's Liberation Army who marched in the celebrations in Beijing that day. He has been speaking to Yashan Zhao about the optimism and excitement of that time.Photo: An officer reads a newspaper to soldiers while they are waiting for the announcement of the foundation of the People's Republic of China on Tiananmen Square on October 1, 1949 in Beijing, China. (Credit: Visual China Group via Getty Images)

In September 1984, the famous Spanish matador, Francisco Rivera, also known as Paquirri, was gored to death by a bull during a fight in the small town of Pozoblanco. The bravery he showed during his final moments turned Paquirri into a legend. In 2013 Simon Watts spoke to El Soro, a matador who shared the bill that fateful day, and to Muriel Finer, an American journalist married to a Spanish bullfighter.Photo: A recent bullfight (Getty Images).

In September 2008, the world's biggest science experiment, the Large Hadron Collider, was started up for the first time at the European Organisation For Nuclear Research, or CERN, in Geneva. Simon Watts talks to Paul Collier, a British engineer whose team built the multi-billion dollar machine designed to investigate the structure of the universe.PHOTO: Inside the Large Hadron Collider (Getty Images)

When the Islamic State group took over Mosul in Iraq in 2014 they flooded the internet with propaganda, claiming life under IS was fantastic. One historian living in the city decided to post a counter-narrative online. Omar Mohammed set up "Mosul Eye" to expose the atrocities and failings of IS fighters, but it was at great risk to his own safety. Omar tells Rebecca Kesby how he posted news from Mosul to the outside world from right under the noses of the Islamic State group. He says he felt it was his duty to tell the real story.(Photo: Mosul Eye website. BBC)

Theodor Wonja Michael was a child when Hitler came to power in Germany. The son of a German mother and a Cameroonian father he faced discrimination and danger under Nazi rule. He has been speaking to Caroline Wyatt about how working as a film actor helped him to survive World War Two.Photo: Theodor Wonja Michael at the Frankfurt Book Fair in 2013. Credit: Alamy

The Rodgers and Hammerstein musical was first performed on stage in New York in 1959, several years before it was made into a film. Vincent Dowd has been speaking to two people with connections to the original Broadway production. Tim Crouse is the son of Russel Crouse who wrote the book for "The Sound of Music". Lauri Peters played the eldest daughter of the von Trapp family on stage. Photo: The original Broadway cast of "The Sound of Music" in 1959. Lauri Peters is at the top of the stairs. Credit: Bettmann/Getty Images

Sir Anthony Blunt, a distinguished British art historian and curator of the Queen's pictures was exposed as a former Soviet spy in the autumn of 1979. He was stripped of his knighthood and publicly shamed as a traitor for being part of the Cambridge spy ring. Susan Hulme has been speaking to Christopher Morris who was the BBC reporter sent to interview Blunt when the story broke.Photo: Sir Anthony Blunt at the press conference in which he explained his motivation in 1979 (Credit: Aubrey Hart/Getty Images)

The first book in the Chronicles of Narnia series by the Northern Irish-born writer CS Lewis was published in autumn 1950. The Lion, the Witch and the Wardrobe would go on to become one of the great classics of children's literature. CS Lewis's stepson, Douglas Gresham, talks to Louise Hidalgo about the academic and theologian who created Narnia's magical world.Picture: CS Lewis, the children's and theological author, seated in his Cambridge study in the early 1950s (Credit: Camera Press/Arthur Strong)