At 18, the maharaja has such a large tummy that he needs an elephant-keeper’s help to make love to his queen.

By 35, the now-slim and refined globe-trotter who dines with Europe’s royalty has plucked a 17-year-old flamenco dancer off a Madrid nightclub and made her his fifth and favourite wife.

Fifteen years later, the forward-looking ruler of Kapurthala is advised on his divorce by a brilliant lawyer named Mohammed Ali Jinnah when he catches his Spanish queen getting pregnant by one of her stepsons.

Racy enough for Hollywood star Penelope Cruz to want to bring the tale to the world’s movie theatres with herself in the lead role.

Yet, how much is truth and how much embellishment?

The tumultuous marriage of Maharaja Jagatjit Singh and Anita Delgado, regular tabloid fare during their lifetimes, is igniting passions a century after their fairytale union, with a Spanish novelist penning their “true story”.

The maharaja’s great-grandson, Shatrujit Singh, plans to sue Passion India author Javier Moro for slandering the family with his “pack of lies” and threatens to block its filming by Cruz.

Moro’s defence is that he “sacrificed the historic(al) truth for the truth of fiction” to be able to “better imagine what went through the heads and hearts of the characters”.

Sure enough, he is ready with his take on the allure the white woman holds for Indian royals: “So it is not surprising that all well-born Indians, swayed by the teachings of the Kamasutra, have dreamed at some time or other of having relations with European women. Having a white woman was considered as an exterior symbol of great luxury and exotic splendour.”

But he also concedes that the well-travelled Jagatjit, with his cosmopolitan tastes, would have found no real companionship among his virtually purdah-bound Indian queens.

For him, it was love at first sight when he saw the Madrid café owner’s daughter — “tall, with clear skin and very black hair, huge sleepy eyes” — swirl at a club.

Persistent requests, assurances and gifts break down the Delgado family’s resistance to the idea of giving their daughter away to a foreigner with a harem. But the ecstatic maharaja is careful to get Anita groomed in etiquette, fashion and stately duties in Paris before she can land in Kapurthala for the wedding with his child in her womb.

Her first few years as Maharani Prem Kaur — her new name though the British never accepted her as Kapurthala’s queen — are a whirl of travel, parties and jewellery.

She makes a splash in Indian high society, has the Nizam of Hyderabad eating out of her hands and, over the frowns of the disapproving British rulers, charms the bonnets off their wives.

Five years later, the romance is dead when the prince’s roving eye settles on an Englishman’s wife. But it’s almost another decade before the increasingly lonely Anita falls for stepson Kamal.

“The man is a volcano of activity,” Moro writes. Kamal is a people’s prince. He goes to the villages every morning and speaks to farmers; he persuades his father to create a cooperative and a system of soft credits for the farmers.

But when the affair is out, he isn’t man enough to run away with Anita leaving behind his privileges.

One particularly sore point with Jagatjit’s descendants is Moro’s claim that the maharaja forced Anita to abort her illegitimate child, at a risk to her health, before divorcing her and packing her off to Europe with son Ajit and a generous allowance. There she lives for nearly 40 years, a picture of Kamal always at her bedside, till her death in 1962.

Jagatjit continues to visit Anita during his Europe trips, although even before her departure he has taken in a French mistress, Arlette Serry. Later, he marries a Czech actress. She, however, decides to jump off the Qutab Minar with her two poodles a few years later.

Jagatjit’s descendants think Moro has done a hatchet job on the maharaja, and sure enough the author delights over his — and other Indian princes’ — whims, weaknesses and bizarre sexual habits.

Patiala’s Bhupinder Singh has an “insatiable sexual appetite”. More than a page is devoted to his surreal tantric orgies involving naked virgins — the high priest pouring wine over their heads for Bhupinder and his guests to suck the trickle off their skin.

Yet Jagatjit is saluted as a “great man” who turned Kapurthala into India’s most advanced state, making female education compulsory, rooting out crime and corruption, keeping communal peace and even giving industry a leg up.

Moro’s aim of portraying “the India of the last days of the Raj” isn’t worth more than a few paragraphs on Nehru and Gandhi — “that madman” to Anita. There are passing references to Amrit Kaur, the maharaja’s niece who always stands by Anita. She later joins the freedom struggle and becomes a minister in Independent India.

However lofty the objective, the book is finally a tale of infatuation and incest. The Jagatjit-Anita alliance has obviously caught warm-blooded Spain’s fancy — there are several other Spanish books on the subject, unlike India where there isn’t a single one.

Did passion die out with the princely states? Maybe it’ll need a Penelope Cruz to arouse it again.