Every schoolchild learns Henry VIII had six wives but not many people know about the sex, sibling rivalry, social climbing and royal intrigue that surrounded the lustful king.

In a tale worthy of a bodice-ripping blockbuster, a woman rises from nowhere to be the king's mistress and bears his child.

With breath-taking arrogance, the woman's sister arrives on the scene, tempts the royal suitor away and goes on to become Queen of England.

The sisters in question are the Boleyns, Mary, who loved and lost, and Anne, who stole the king's heart but finally lost her head.

The story is soon to be told in a TV drama The Other Boleyn Girl.

The BBC programme is based on a book by best-selling author and broadcaster Philippa Gregory.

Philippa, a former Sussex University student, was living in Midhurst when she researched the book.

Her detailed research has left her with an admiration for Anne.

"She is ambitious, determined, cruel and criminal - she is implicated in the poisoning of three men. She also had the most appalling temper. And she literally takes the king from her own sister, sibling rivalry at its most extreme.

"But you can't help but admire her, getting herself from virtually nowhere to being the queen of England.

"Mary, on the other hand, is the absolute reverse. She chose to marry for love, which is a fascinating choice. She even writes a letter about her right to marry in the most passionate terms."

The film explains how the happily-married Mary is forced by her ruthless family to become Henry's mistress after catching his eye at court.

Initially horrified by her predicament, she quickly falls in love with the young king. But while she is pregnant, the king's wandering eye turns to her ruthless sister and Anne's scheming relations make Mary step aside so Anne can manoeuvre herself into becoming queen.

Philippa spent two years researching and writing the book, visiting venues like Hever Castle, Hampton Court, Greenwich and the Tower of London, and another two years overseeing its adaptation to the small screen.

She is delighted with the TV production, which stars Jodhi May as Anne, Natascha McElhone as Mary and Jared Harris as the king.

Philippa, 49, said: "When you move from one art form into another, there are going to be changes and I had some worries, particularly as it was a period piece and some historical dramas get stuck in the costume and it can look almost like pantomime.

"But I'm very pleased with it. It looks stunning and it has been shortlisted for the Cannes Film Festival."

Philippa's love of history and background in journalism - she worked in newspapers and radio - have opened up many doors for her.

She makes regular contributions to national newspapers and magazines, writes short stories and works in TV and radio.

She said: "There is such a lot of interest in history and because I am not an academic specialist, I'm not trapped in one period. I will have been with the Tudors for two decades and there's probably a third to come but it's such an incredibly interesting period."

Philippa's new book, The Queen's Fool, is out in November.

The Other Boleyn Girl will be shown on BBC2 on March 28.