By Robin Millard
Queen Victoria and Queen Elizabeth II, Britain's longest-reigning monarchs, both came to the throne young yet remained a steady presence through eras of dramatic change.
Queen Elizabeth will overtake her great-great-grandmother's record of 63 years and 216 days on September 9, a remarkable reign that began in 1952 as Britain rebuilt after World War II.
When Victoria was born in 1819, she, like Elizabeth, was thought unlikely to inherit the throne.
Yet the young princess, who became queen in 1837 shortly after turning 18, lent her name to an age of invention and discovery, as well as a moralistic outlook on life.
The Victorian era was a time when Britain was at its zenith, making grand industrial, scientific, cultural and imperial advances.
The roots of 89-year-old Queen Elizabeth's duty-driven style of monarchy lie with her illustrious ancestor.
"The great similarity between Elizabeth and Victoria is that they're both exceptionally conscientious, strong-minded women, determined to do it absolutely as correctly as they could," writer Andrew Gimson says.
The only child of Prince Edward, the fourth son of king George III, Victoria was born fifth in the line of succession.
But the late Edward's elder brothers, including George's successors George IV and William IV, all died without surviving legitimate children, leaving Victoria to inherit the throne.
Born at Kensington Palace on June 24, 1819, Victoria was brought up under the "Kensington System", a series of rules invented by her mother that kept her isolated and constantly monitored.
On inheriting the throne, she set about changing how the monarchy operated.
"It had fallen into very low repute under her wicked uncles who behaved in the most disreputable fashion," Gimson says.
"Victoria plugged into this new middle-class morality, the moral earnestness which was emerging in the 1830s."
On becoming queen, she was mentored by Prime Minister Viscount Melbourne and sidelined her overbearing mother.
She married her German first cousin, Prince Albert of Saxe-Coburg and Gotha, in 1840 and was besotted with him. She survived the first of several assassination attempts later that year.
When Albert died in 1861, she plunged into mourning, retreated from public view, and wore black for the rest of her life.
She formed a close bond with her Scottish manservant, John Brown, through the 1860s and 70s.
Amid rising republican sentiment, Victoria began to appear in public again starting in the 1870s.
Victoria's nine children married into continental royalty, making her the "grandmother of Europe".
Her 1887 golden jubilee and diamond jubilee in 1897 were celebrated throughout the empire, with Victoria seen to embody British greatness.
States, cities, mountains, lakes, streets, squares, buildings and monuments across the world still carry her name.
"Under Victoria, the British empire was expanding to an enormous extent and she got given this grand title of Empress of India. British power was at its height," Gimson says.
"Under Elizabeth II, the British empire has vanished. She and the whole British nation have had to cope with a period of relative decline, although the standard of living has gone up colossally."
Queen Elizabeth's beginnings resemble those of Victoria and neither was born to be a future queen.
Elizabeth only did so because her father became king after her childless uncle, Edward VIII, was forced to abdicate to marry the twice-divorced Wallis Simpson.
After a somewhat cloistered youth, Elizabeth married Prince Philip, her second cousin once removed.
The great statesman Winston Churchill, who entered parliament in 1900, was the first of her 12 British prime ministers and a mentor.
Victoria got much more heavily involved in politics than Elizabeth would deem prudent, however.
The Times columnist Matthew Parris says Elizabeth "works much harder" than Victoria, but little else has changed since.
"We must not let in daylight upon magic remains the guiding principle," he writes.
Buried in Windsor, west of London, Victoria died in 1901 aged 81, but Elizabeth is still fully active at 89.
She has reigned with the steadfast support of 94-year-old Prince Philip, while Victoria was 42 when Albert died.
Judith Rowbotham, visiting research fellow at Plymouth University, says as she enters her 90s, Elizabeth's reign would likely come to resemble that of Victoria in mourning.
"We're actually going to enter a phase where the similarities between the two become much more acute," she says.
"We're used to seeing the Queen actually doing things. We're used to seeing her turn up to open things. Victoria received state visitors and kept royal diplomacy going, but in a way which was much more static."