I couldn’t let this occasion pass without celebrating the life and work of author and journalist Gitta Sereny, who died earlier this month aged 91. In an era distinguished by the ersatz she was that rarest of things, the real deal, a giant among pygmies.

Her books on Mary Bell, the child murderer, Franz Stangl, commander of the Treblinka death camp, and Albert Speer, Hitler’s architect and war minister, are landmark studies which will never be surpassed. But they go beyond even this to transcend questions of genre and history: put simply, they are books without which it would be impossible to fully examine the tortured moral landscape of the 20th Century, or indeed of the human soul.

In her excellent book of essays, The German Trauma, Sereny recalls attending one of Hitler’s Nuremburg rallies as a child, quite by chance. It seems as if destiny came calling early.

Many authors have looked into the heart of darkness that was Nazi Germany. One thinks of Primo Levi, or more recently Martin Amis and Jonathan Littell, whose novel The Kindly Ones is certainly a very powerful read. But few addressed, so unflinchingly, the central question of human behaviour that this era poses.

Her book on Stangl and Treblinka, based on hours of interviews with the man, was, as its title proclaimed, a harrowing journey into that Nazi darkness, and it turned on what is still an essential conundrum of human nature. Namely, how is it possible that an ordinary person can become a mass murderer, and still be at ease with his conscience?

Lest we forget, Treblinka, the most terrible of death camps, was where nearly 800,000 Jews were murdered in a matter of months – only around 60 survived. This book was also distinguished by Sereny’s examination of role of the Vatican in aiding many top Nazis to flee to South America.

Sereny’s controversial books on Mary Bell were once again borne out of her preoccupation with human nature. How and why did Mary Bell become a murderer? Sereny’s examination of Bell’s appalling childhood provided one explanation. Here too she proved herself to be a forerunner.

Today, we are much more cognisant of the sheer extent, ubiquity and psychological consequences of child abuse – and in part we have Sereny to thank for that.

I was fortunate enough to meet her once, at the Edinburgh Book Festival, where she was due to talk about her book on Speer. I’m fairly blasé about meeting authors, however ‘big’, but not this one. I approached her with knees knocking – but found her charm itself, and very kind to a tongue-tied, star-struck fan.

The book on Speer is simply extraordinary. Based on a huge amount of painstaking research, and eleven years of knowing and interviewing Speer, it will undoubtedly stand as one of the greatest biographical and psychological studies ever written.

Again it was controversial. Despite getting Speer to admit what he had spent years denying – that he knew nothing of Hitler’s Final Solution - critics complained that Sereny had been ‘seduced’ by Speer, and that in professing her liking for him she had given up her objectivity. At times the book is indeed disconcerting for this reason.

But critics were not reading it carefully enough, nor were they sufficiently alive to the absolute mastery of her literary approach. The whole book is ultimately about moral equivocation, (Speer’s ‘Battle with Truth’), and her stroke of genius was to include herself as a protagonist in that equivocation, by accepting the intricate pas a deux that Speer invited her to dance with him.

This technique results in a brilliantly tangible means of representing and enacting the drama of conscience, truth and falsification that constantly took place within Speer’s mind:  as readers we don’t just observe it, we feel it.

At the same Book Festival I put this point to Hans Magnus Enzensberger, acclaimed writer of post-war German letters. “She loves Speer!” I proclaimed. He looked at me and smiled. “Yes”, he replied, “but on purpose – no?”