While she was recuperating from a skiing accident in 2013, Angela Merkel picked up a 1,500-page tome on the 19th century by the historian Jürgen Osterhammel called The Transformation of the World. The book left an impression. A few months later she invited Osterhammel to her 60th birthday party, not just to celebrate but to give an hour-long lecture.

The theme was “history and time”, and those familiar with Osterhammel’s work detect his influence in Merkel’s worldview, particularly where he covers globalisation, migration and technology.

The admiration is mutual. “Even though I am not a member of the CDU [Christian Democratic Union] and an old SPD [Social Democratic party] voter, I am a personal fan of the chancellor,” Osterhammel said in an email exchange with the Guardian. 

“Few people are likely to have read my book from beginning to end,” Osterhammel admits. “They don’t have to, and I hope the chancellor didn’t. There are many other important books to learn from. The amazing thing is that senior politicians do read history books at all.”

The historian rejects the idea that his book has had a direct influence on Merkel’s policies. But many sections of the work – on globalisation, migration and technology, to name a few pertinent topics – read differently in the light of decisions she has made since reading it, such as the treatment of Greece at the height of the eurozone crisis. ...