Olivia Colman on Who Do You Think You Are?: Everything you need to know

The award-winning actor Olivia Colman is, by her own estimation, “the least adventurous person I know”, someone happiest “at home, in my pyjamas, with my family”. Somehow, it seems in keeping with this self-image that generations of her father’s family should have come from Norfolk. Yet, as Olivia finds out when she traces her maternal forebears, said to include a French woman, that’s by no means the whole story.

Her first stop is Norfolk, where Olivia meets her parents and her uncle, Richard, who has drawn up a partial family tree. Two names in particular jump out in her maternal lineage - her 4x great grandparents Richard Campbell Bazett and Sarah Bazett. Richard, she learns, was born on the tiny island of St Helena in the South Atlantic and worked in London and Calcutta for the East India Company.

In London, Olivia learns more about Richard’s life. He dealt with large sums of money and was married twice, his first marriage ending in divorce in 1809, a rarity in an era when divorces had to be granted by an act of parliament. While Richard divorced his first wife, Margaret, on the grounds of her “open adultery” with a harpist, it turns out his first two children with Sarah, including Olivia’s 3x great grandfather, were born before the couple were married. “What a hypocrite,” says Olivia.

Tracing the life of Charles, Olivia begins with the 1871 census, which show him as a retired Lieutenant Colonel living in Reading. His wife, Harriot, the document reveals, was born in Kishanganj, north-east India, Olivia’s next stop.

Harriot’s life story is remarkable. Her mother was Indian, but Harriot was sent to England at the age of around three, travelling alone, following the death of her father, William Slessor, a military man killed when his gun misfired. There’s no trace of her mother in the records, but a will reveals that her great aunt, Louise Girardot, bequeathed Harriot £800. Some of the money she spent on returning to India, where she married following a shipboard romance.

But within a year, her husband, William Trigge Garrett, died, aged just 29. Back in England, she met Charles, whom she had previously turned down. Touching letters from Charles reveal details of the couple’s courtship. They had four children together, all born in India.

To complete her picture of Harriot’s life, Olivia heads for the Scottish Highlands. Here, she meets Geordie Burnett, another descendent of Harriot’s grandmother, Harriot Elizabeth Slessor. Through Harriot Elizabeth’s extensive diaries and letters, which have been typed up, Olivia learns that Harriot’s family dearly loved the granddaughter nicknamed ‘India’ Harriot, which must have helped Harriot deal with her life’s many setbacks.

There’s another revelation, Harriot Elizabeth’s mother was called Anne Judith Bristow and Geordie has a portrait of her. A naturalisation document reveals she was born in Paris, a French Huguenot. “She’s the French woman! Oh my god!” says Olivia.