Mao Zedong and Zhu De, a military leader, pictured here during the late 1930s. [Photo provided to China Daily]

"History teachers have got in touch, saying they are using it as a way of making classes more engaging, and the really good thing is that they say looking at the pictures is then encouraging pupils to go off and do more reading about the subject," she said. "They're now interested in learning about things which they previously didn't even know about, so it's great to see that reaction."

Jones says this is exactly the response he was hoping for.

"For me, the watchword was always 'accessibility' – apart from a few images of scenes like Nazi concentration camps and dead bodies, this is a book my nine-year-old child can dip into. I think it's suitable that it could go into any secondary school library, and anyone with an interest in modern history would enjoy it, and in the case of topics such as Chinese history, come away feeling they've really learnt something from it."

Beauty is in the eye of the beholder, so everyone will have their own favorite image from the book, but for the authors, things are not so clear – or, one could say, black and white.

"My favorite image still has to be the Lewis Powell one, that started the whole project off," says Jones. "That's what gave me the first hit, when something short-circuited my brain between the age of the photo and the immediacy of the gut reaction it produced. I knew this was something special."

"I can't really choose one," said Amaral. "The picture of the nine kings (nine European monarchs gathered together at the funeral of British King Edward VII in 1910) took me such a long time to complete that when it was finished, it was very special, but choosing just one out of all these amazing pictures? It's like asking me to choose a favorite child."

The Colour of Time: A New History of the World, 1850-1960 is published in the UK by Head of Zeus.