As the future ruler of an island situated between France and the United Kingdom, she learned standard French and the local Sercquiais dialect of the Norman language.

[3] At the age of 15, Sybil fell in love with Dudley Beaumont, a British painter who could neither shoot nor climb cliffs, and who her father therefore considered a "weakling".

Wanting to be reconciled with his daughter, her father sent her a telegram of congratulation which contained words of consolation as well, as the child was female: "Sorry it was a vixen".

Sybil went on to have six children more: four sons – Francis William Lionel, Cyril John Astley, Basil Ian (died in infancy) and Richard Vyvyan Dudley, and two more daughters – Douce Alianore Daphne and Jehanne Rosemary Ernestine (born posthumously).

[5] Dudley Beaumont, who served in the British Army as an officer during the First World War, died on 24 November 1918 during the Spanish flu pandemic.

[2] Neither her father nor her father-in-law, the army officer William Spencer Beaumont, were willing to give financial support to the widow and her six surviving children.

She thus banned motor vehicles and holiday camps, but the Chief Pleas refused to pass an ordinance that would forbid selling alcohol to anyone known to get drunk.

While Appointment with Venus was being shot on Sark in 1951, the Dame even deigned to allow a car ashore, ostensibly believing that "a Land Rover was some sort of senior Boy Scout".

[2][6][7][8] Robert was not aware that the marriage made him jure uxoris seigneur of Sark, his wife's co-ruler, until they set foot on the island.

[2] Lecture tours in the United States, aided by her second husband's connections, were part of her efforts to promote tourism and bring more revenue to the island.

[2] Most of her tenants bitterly resented her for the decision to remain on Sark during the ensuing five years of occupation, but thanked her after the war when they saw how total evacuation destroyed the neighbouring island of Alderney.

[10] The Dame had her senior official meet German officers at the harbour and escort them to her residence, where her maid announced them as if they were guests.

[11] Hathaway was much respected by the islanders as well as by the Germans, whose language she spoke perfectly, for the leadership she gave during this period, and the British Home Secretary Herbert Morrison observed that she remained "almost wholly mistress of the situation" throughout the occupation.

Hathaway was on friendly terms with Eugen Fürst zu Oettingen-Wallerstein [de], the German commander stationed in Guernsey, as indicated by their warm correspondence.

[14] According to British historian David Fraser, Sibyl did not raise her objection to a series of antisemitic orders that had been previously issued by the German authorities, which concerned among others her Czech Jewish friend Annie Wranowsky.

[5] On the 400th anniversary of Queen Elizabeth I's grant of charter signed in 1565[18] to Sark's first seigneur, Hellier de Carteret, Hathaway was made Dame Commander of the Order of the British Empire at Buckingham Palace.

At the same time, she had a sharp dispute with the Chief Pleas, claiming that its members violated the laws they themselves had passed and that their misconduct threatened to make her tourism campaign futile.

Early next year, the 90-year-old gave her approval for the stage presentation of William Douglas-Home's play The Dame of Sark, inspired by her experiences in the Second World War.

She looked forward to meeting Celia Johnson, who was to play the title role, but died suddenly at the Seigneurie of a heart attack on 14 July 1974.

The seigneurship passed from the benevolent dictator,[11] referred to as a "lady of unusual personality" by a British government official, to her grandson Michael Beaumont.