Then again, the 18th-century lovers’ handbook given to Princess Margaret on the day that she ended her relationship with Peter Townsend is an unusual book.

The curiously titled The Delights of Wisdom Concerning Conjugial Love — After Which Follows the Pleasures of Insanity Concerning Scortatory Love is among 550 books once owned by the Queen’s sister that will be sold at auction next month.

Inside the hardback, which was opened to The Times yesterday, the author muses over “the pleasures of the flesh” and the “filthiness of fornication”. There is also a typed inscription dated October 31, 1955 — the same day that the 25-year-old Princess issued a statement saying that she had no plans to marry her first love, a divorcé.

It is not known who gave her the book, which also gives advice on betrothals, weddings, and the etiquette of second marriages. A note on the inside cover reads, “To Margaret, Princess of the Realm”, and is signed with the initials “WM”.

Beside it, someone has doodled a drawing in pink ink of a dove apparently dive-bombing through clouds towards a symbol resembling a Christian orb.

The coincidental timing of the gift was spotted by organisers as they prepared the five lots for a sale of books on October 5.

Rupert Powell, managing director of Bloomsbury Auctions, said: “We really do not know who WM could be. Obviously this was a date of huge significance in her life, so this is an interesting book to be giving her on that day.”

The work, written in 1768 by Emanuel Swedenborg, a Swedish scientist and philosopher, examines the spiritual side of sexuality, and includes colourful chapters on “jealousy”, “fornication” and “the lust of defloration”.

Exploring philosophical and religious themes, it distinguishes between purity of monogamous sexual relations within marriage and the less virtuous — but no less enjoyable — “delights of scortatory (or fornicatory) love (that) commences from the flesh”.

Princess Margaret’s friend Noël Coward wrote of her much publicised personal crisis as she chose between love and the royal life: “Apart from Church and royal con- siderations, it would have been an unsuitable marriage anyway. She cannot know, poor girl, being young and in love, that love soon dies and that a future with two strapping stepsons and a man 18 years older than herself would not really be very rosy.”

The lots, which will be sold collectively with other books of dubious literary merit, are expected to reach about £1,500 — a far cry from the £13.5million windfall enjoyed by the late Princess’s son, Viscount Linley, whose auction of his mother’s belongings this summer exceeded all expectations. Also included in the sale are pulp fiction novels, an academic essay, Racism and Its Elimination, signed with “love, devotion and loyalty” from the author, and Margaret’s own personal copy of the biography of Townsend.

While Swedenborg’s work appears unread, the life story of the Battle of Britain hero is described in the auction catalogue as having “finger-soiling” and a “fading spine”.

Loving advice

“The state of a widow is more grievous than that of a widower”

“The conjugial love of one man with one wife is the precious jewel of human life”

The text says that a girl must defer to her parents’ will when choosing a suitor because “they are more advanced in age, and age improves judgment and gives clear sight in regard to suitableness and incompatibility”

Women’s judgment is clouded by feelings “arising from the senses, and not as yet the desires arising from a cultivated mind”. If women do not defer to their parents, they risk “prostituting their modesty”

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