29/10/2014 05:51 GMT | Updated 29/12/2014 05:59 GMT

Writing 'Belle' Was Not Always Easy

When my publisher called me to ask me to write an 'accompanying' book for a forthcoming Hollywood movie I asked the only two sensible questions an author should ever ask. How long have I got? How much am I being paid? I have always subscribed to the Dr Johnson belief : 'No man but a blockhead ever wrote except for money'. One of the answers to the above was satisfactory so I got my head down over the summer and wrote like a demon.

The movie in question was Belle. An intriguing story about the slave trade in 18th century Britain and a woman who helped to change the course of history. Dido Elizabeth was a beautiful, mixed-heritage girl who was brought up at Kenwood House in Hampstead by Lord and Lady Mansfield. She was their half-niece, and she became their adopted daughter. So how did a beautiful, black girl come to be raised as an aristocrat in England at a time when the country was getting rich on the profits of the slave trade? Why had her story never been told? Did she influence Lord Mansfield, Lord Chief Justice, in his pioneering 'Somerset' judgement, which was seen to be the starting point for the abolition of the slave trade?

These were just some of the questions my book set out to answer. But first I wanted to know why the film producer and director had sought me out. Damian Jones, the executive producer, had discovered that I knew a little about Dido Belle. I had recently published a new biography of Jane Austen. I wanted to construct my biography in a more innovative and interesting way than all the other tellings of Austen's life, so I structured it around objects, a piece of jewelry, an Indian shawl, a writing desk, a portrait. Well, the portrait I chose was a fascinating double portrait of two beautiful girls. One was flaxen-haired, with pale skin and blue eyes, wearing a pink silk dress. But behind her, almost running in the wind, was one of the most gorgeous girls I had ever seen. She was expensively dressed in an exquisite gown of ivory satin and a bejeweled turban, out of which poked a fashionable ostrich feather. A cluster of creamy pearls encircled her slender neck. She wears expensive droplet pearl and diamond earrings. She is in motion, bursting with life and vitality. She is also mixed-race. This was clearly a highly unusual commission. In what circumstances did this girl come to be painted as an equal to the white girl and what was their relationship?

I knew that Jane Austen knew the white girl in pink. She was Elizabeth Murray and she married a friend of Jane Austen's brother. Jane Austen met this Elizabeth on a few occasions. She found her rather dull. I suspect she would not have found Dido dull.

So I wrote a little about Dido and Lord Mansfield and the slave trade. My favourite novel is Austen's Mansfield Park, a novel with the slave trade as its 'shadow story'. So when I got the call to write the book, I was so excited to be able to plunge a little deeper into this story.

Writing Belle was not always easy. Some of the gruesome stories about the horrors of the slave trade, most taking place on the 'slavers', were sickening to read and write about. Dido Belle's mother was a beautiful slave called Maria, and she was captured by naval hero, Sir John Lindsay. Their child was born and Lindsay brought her to England and asked his uncle, Lord Mansfield, to raise his child. The Mansfields were childless. They raised Dido alongside their niece, Elizabeth Murray, who was close to Dido's age. They were raised as sisters. The double-portrait is a tribute to their extraordinary bond. Elizabeth is pulling Dido into the frame, holding out her arm to her whilst Dido smiles enigmatically and points a finger to her dimpled cheek. A reference to her colour, perhaps.

We don't know many facts about Dido, so fleshing out her story was a huge challenge. I was worried too about how I would feel when I saw the film. This was a true story. How many distortions, embellishments, outrages would have visited on the narrative? Would it have a 'Hollywood' ending. I need not have worried. The film is a triumph. I cried at the end, and I felt proud to have been connected with this unique and moving story.

'Belle' is available on Blu-ray and DVD now