Author David Waller’s latest book The Magnificent Mrs Tennant, a biography of Victorian hostess Gertrude Tennant, was the runner-up in the Biographers' Club Prize last year, and he will be discussing how he pieced together his account of a remarkable life at the Richmond Lending Library on February 23. He spoke to Will Gore ahead of the event.

Why did you pick Gertrude Tennant as the subject for your latest book?

It was really the other way round - in a sense she picked me. I was lucky enough to find two chests in an attic, both full of her diaries and letters. Having found all that I had no choice but to write this book.

What was the most surprising thing you discovered about her?

The depth of her friendship with Gustave Flaubert, one of the greatest writers of the 19th century. I found 25 original letters which showed they had a passionate friendship. I wouldn't go so far as to say they had an affair, but they certainly kissed at the Paris opera!

What have you got planned for the Richmond library event?

I will explain the circumstances of the discovery then give an overview of a remarkable life that began in1819 and ended nearly a century later, in 1918.

What makes the Victorian era so fascinating to you?

The Victorians achieved so much in every field - literature, science, industry, politics etc. They were extraordinary achievers but underlying all of this there was doubt and uncertainty. They are much more sympathetic people than we often imagine.

What is the key to a good biography?

To make the reader feel understanding and sympathy for the subject, and to place the subject in its historical context without making him or her a mere device for writing about the historical period in question.

What is the biggest pitfall to avoid in writing a biography?

Losing a sense of the story and getting bogged down in the details.

Who else would you like to write a biography about?

Eugen Sandow, Victorian body-builder.

What inspired you to become a writer?

A period of profound boredom in the office led me to do a part-time history degree at Birkbeck. Then one thing led to another.

Best biography you've read

Richard Holmes on Coleridge. Also A Bit of a Blur by Alex James.

David Waller, Richmond Lending Library, February 23, 6.30pm, free. Places by calling 020 8940 0981 or visiting richmond.gov.uk/libraries