The individual without whom one of the most highly anticipated political memoirs in years might not have happened is Beate Baumann. The 61-year-old has worked at Merkel’s side for over 30 years, having first been recruited by her as an office manager. When Merkel retired in 2021, Baumann, it was understood, would continue by her side, but from now on under the revised title of “political adviser of the out-of-service German chancellor”.

Once she had decided to write about her life, Merkel acknowledges in the foreword, she recognised: “If I was going to do it at all, I had to do it properly, I said to myself, and if I was, then I would do it with Beate Baumann. She has been advising me since 1992, and is an eyewitness.”

The secrets of the women’s working partnership, unusual in particular for its longevity, remain largely unknown to the public. Intriguingly, it is reported that despite their decades-long collaboration they still use the polite “Sie” form to address each other, rather than “du”.

Baumann has declined to participate in interviews to coincide with the publication of the 720-page tome, just as she avoided sharing any of the limelight while Merkel, 70, was in power. Although sometimes recognised on the street, she has acknowledged avoiding small talk. On Tuesday night, when Merkel introduced her book to a German audience for the first time at the Deutsches Theater in Berlin, Baumann chose to remain backstage.

Angela Merkel at the presentation of her autobiography at the Deutsches Theater in Berlin. Photograph: Stefan Boness/Ipon/Sipa/Rex/Shutterstock

“Anyone who sees Merkel and Baumann together feels their familiarity, which is not only expressed in the frequent eye contact between the two. Baumann often nods when Merkel has barely begun her sentence,” wrote the journalist Melanie Amann in the latest edition of Der Spiegel.

For their joint writing project they founded the company “teaMBook GbR” (“M” for Merkel, “B” for Baumann) and rented a small working apartment in Berlin-Mitte. The company structure was to help with tax duties – as a civil servant, Baumann’s role as author has to be separated from her job as political adviser to the former chancellor.

Insiders say that by day the duo typed the manuscript in the apartment on computers that were not connected to the internet, and in the evening saved the contents on a USB stick and locked it in a safe.

Nothing was left to chance. They wrote the volume together, choosing which events and people to include or omit, shaping the contents of each chapter, with one of them writing the first draft, which the other then typically revised. They did not turn to ghost writers or rely on historians or journalists. Neither did they recruit an agent, but instead negotiated the publishing deal – an undisclosed sum, but thought to run to several million euros – themselves.

Angela Merkel, with Beate Baumann, arrives for a round of coalition negotiations with the German Christian Democrats and the Bavarian Christian Democrats in November 2013. Photograph: Michael Gottschalk/Photothek/Getty Images

Merkel was even spotted some mornings picking up pastries in the local bakery near their working flat, in what became part of their daily routine over the more than two years it took them to complete the book.

Sometimes, for a change of scene, they retreated to Merkel’s modest rural retreat in Templin, in the Uckermark region of Brandenburg, at others they escaped to the Baltic coast. Two beachside hotels in the dunes of the picturesque Darß peninsula are acknowledged in the book.

When Merkel was in power, they had separate offices overlooking the Tiergarten park and the River Spree on the same floor of the chancellery, but on opposite sides of the building. Baumann is quoted as having said: “I need my peace”.

The key to their working together, she told Amann in 2021, was “to be in constant conversation”. Their rules: never cover anything up, never shoot from the hip.

Copies of Angela Merkel’s memoir. Photograph: Clemens Bilan/EPA

A graduate of English and German, from the north-west city of Osnabrück, Baumann was 29 when she was first recommended as an aide to Merkel. She said she hadn’t needed the job and had been toying with becoming a school teacher, so was particularly relaxed when it came to meet Merkel, who was laid up at the time, having broken her leg. She found her open-minded and approachable. The rest is history.

She has followed Merkel more or less from her political beginnings, when she became environment minister, then general secretary of the Christian Democrats, party leader, parliamentary head, and then chancellor, four times. The whole of this time Baumann was referred to simply as “the office manager”, even if it has long since been acknowledged that her role was far greater.

Described as funny, charming and quick-witted, she is said to have been annoyed over the years by various fictional versions of Merkel. One particularly pernicious rumour was that the “office manager” poured the coffee, when in fact, she said, that’s what Merkel has always done herself.