Queen Elizabeth II's strict bedtime routine saw the monarch clocking in at least eight and a half hours of sleep every night. Her nightly ritual saw Her Majesty hit the pillow no later than 11PM, rising at around 7.30AM for a busy day of engagements.
The same can't be said for the late monarch's son, however. King Charles, 75, known for his heavily plant-based diet, love of gardening and military-style exercise routine, somehow manages to cope with very minimal sleep - according to those closest to him.
Sophie Winkleman, known as Lady Frederick Windsor, reflected on her close relationship with the King in a new interview with Tatler, alluding to the monarch's peculiar sleep cycle.
"He works all day long, has a quick supper and then disappears until about 4am to write letters," she said. "He cares about so many things and he comes up with brilliant solutions."
Sophie's insight isn't the only revelation we know about Charles being a night owl as a result of his work.
In royal commentator Robert Hardman's new book Charles III New King. New Court. The Inside Story., the Princess Royal, Charles's younger sister recalled the period of time after her brother's investiture as the Prince of Wales in July 1969.
Princess Anne recalls the aftermath of the event, which led the then-Prince Charles to be so burnt out he needed to be sent away to recover.
"We were sent off to Malta for him to recover. He really did need to recover," said Princess Anne, who recalled that the constant walkabouts had left her brother so exhausted that he was doing them in his sleep. "He woke up trying to speak to people," she added.
King Charles' wife Queen Camilla reportedly has told the monarch he "needs to slow down a bit" in the wake of his recent bout in hospital, which saw him undergoing surgery for an enlarged prostate, per The Sun.
What King Charles' bedtime routine lacks in structure, he certainly makes up for in his daily schedule. There is no "average day" for the sovereign who carries out more than 609 royal engagements a year as reported in the Telegraph.
Princess Diana’s former butler Paul Burrell also revealed in documentary 'Serving the Royals: Inside the Firm', that His Majesty was incredibly particular about his baths.
"The water temperature has to be just tepid," he said, adding that the tub can only be "half-full" with its plug "in a certain position."
The monarch also famously skips lunch, with the view that eating a midday meal is a "waste of time" and a luxury that uses up precious energy he could be using to work.