Judith Flanders has never played video games – not even Angry Birds – so no one was more surprised than the historian herself when she was approached by the developers of the Assassin’s Creed franchise to serve as a consultant on the latest instalment, set on the streets of 19th-century London amid the Industrial Revolution.

“It’s like you’re an expert on a faraway place,” said Flanders. “You’ve learnt the language. You’ve met people from there. You’ve read every single book that was ever written. Now,...