As the doyenne of the historical novel and a respected expert on the dark deeds of the rulers of Tudor England, Philippa Gregory knows chicanery and abuse of power when she sees it. Which helps explains why she is vexed by the actions of the Crown against 4,000 of its citizens some 400 years after the reign of Henry VIII.
When she is not researching or writing the next book in her best-selling series about the tempestuous lives of noble (and ignoble) courtiers, consorts and queens, Gregory has found a new outlet for her sense of historical injustice – the exiled inhabitants of the Chagos Islands.
The novelist has become patron of the UK Chagos Support Association as part of her effort to raise the profile of the displaced Chagossians, who were scattered across the globe to locations from Mauritius to Crawley, West Sussex, after the British government forcibly cleared the Indian Ocean archipelago of its human population in the 1960s and 1970s to make way for a key American airbase on the island of Diego Garcia.
At first glance, the plight of the Chagossians is a far cry from the dark castles and absolute monarchs riven by ambition, politics and betrayal which has made Gregory one of the country's most-read authors (to date she has sold at least 12 million books worldwide) and the originator of a Hollywood blockbuster based on her novel The Other Boleyn Girl.
But from the use by the Labour government in 2004 of the Privy Council, the extra-judicial administrative body set up by Henry VIII, to overturn a Law Lords ruling allowing the Chagossians to return home, to the announcement by the Government last year that it was turning the entire archipelago into the world's largest nature reserve, Gregory sees many parallels between Tudor autocracy and Britain's treatment of nationals in the 20th and 21st centuries.
Sat on a sofa in a York bar, her words brimming with indignation, Gregory says: "When it comes to the treatment of the Chagossians, it's as if the democratic revolution never happened. It is totally tyrannical. I cannot understand why successive British governments would act against their own subjects so consistently over so many years using so many underhand techniques.
"The Privy Council was an institution created by the Tudor monarchs to get what they wanted done quickly, without having to consult very much. The administration of the Crown used it in exactly that way with the Chagossians. It was using the Privy Council to endorse Foreign Office-made policy and change the lives of 4,000 people. The abuse of power and cruelty to people who can't fight for themselves is very familiar to me as someone who has studied the Tudors and the Plantagenets."
The role of vociferous campaigner sits well with the history-steeped author, perhaps due to her training as a journalist and a natural rebellious streak. She was born in Kenya but the family returned here when she was a baby after her father, an ex-RAF navigator, died in a plane crash in 1955.
By dint of a move to a farm in the North Yorkshire Moors, where she lives with her family, five horses and "dozens" of ducks, Gregory's MP is by "wonderful coincidence" William Hague. Quite whether the Foreign Secretary sees it that way is unclear since he now receives regular visits to his constituency surgeries from the author to seek face-to-face updates on his efforts to resolve a dispute which Whitehall has successfully brushed under the carpet for nearly 50 years.
With a hint of mischief in her voice, she says: "I like to go along every few months to ask him about the Chagossians. I know William Hague is sympathetic and would like to find a way out. But he is very, very constrained by many years of government policy and is advised by some of the people who made that policy." She adds: "This is about how Britain stops being an imperial power. What happened was absolutely morally wrong."
Although she flinches at the suggestion she has spent her working life fighting one battle or another, Gregory has had to put up with high-brow prejudice against the literary genre that she helped remodel in the last 20 years.
A trained historian with a PhD in 18th-century literature, she makes a point of underlining that historical accuracy is at the heart of her writing.
Her latest novel (following volumes on a succession of figures from Mary Boleyn to Mary Queen of Scots) about the 15th-century Jacquetta, Duchess of Bedford, will be accompanied by a separate academic text she has co-written on little-known figures from the Wars of the Roses. But she says that "massive snobbery" persists against historical fiction with literary critics "top skimming" the genre to declare works such as Hilary Mantel's Wolf Hall as "literature" while ignoring much of the rest.
She says: "I am in the interesting position of being sometimes skimmed by the critics and called literature and sometimes called historical fiction. I like writing historical fiction. I like to do the research of history and the creativity of writing fiction. I am creating this thing which I think is twice as difficult as writing either history or fiction."
Despite being the author of 22 books with translations on sale in 26 countries, Gregory has not received the attention accorded to other titans of the literary establishment. She is far from bitter but in a world where best-sellers rarely get shortlisted for the Booker Prize, Gregory says the values of Britain's literary elite have become questionable.
"You join the literary canon for all sorts of reasons but most of them are not about the quality of the work. Most of them are about other criteria like, I'm sorry to say, your gender, your education, your background and who publishes you... People have got muddled up between accessibility and literary value. At the end of the day, I'm writing in a genre that isn't highly regarded."
She is less keen to discuss her personal life, but says that her attitude to history is partly shaped by the tragedy that marred her early life – the death of her father, Arthur Percy Gregory, known as Greg, who survived 32 missions – the most permitted by the RAF – as a navigator on Lancaster bombers flying across wartime Europe before his passenger plane smashed into Mount Kilimanjaro in thick cloud in 1955.
With a slight catch in her voice, she adds: "It is only in the last six years that I have been able to talk about my father without becoming tearful."