Watch: What is the key to a long life?
Living to 100 was once considered virtually impossible, an age so ancient anyone who made it would be an astonishing outlier.
With strides in healthcare and medication, however, times have changed dramatically.
When the monarch first began to send greetings to centenarians, in 1917, George V sent out just 24 telegram with the words: ‘His Majesty’s hope that the blessings of good health and prosperity may attend you during the remainder of your days.’
By 1952, when the Queen ascended the throne, that had risen to 273 - and by 2014, the office counted 7,517 100th birthday telegrams.
It's no longer a given either, than the recipients will be in a home or hospice - during lockdown, 100 year old Captain Sir Tom Moore raised millions for charity walking round his own garden, and fashion inspiration Iris Apfel, who recently turned 100, still lives and works at her New York apartment, posting regular updates showing her astonishing style on social media.
'Ordinary' centenarians regularly hit local news, too for their active lives and fundraising. Recently, a 100-year-old man from the Isle of Wight swam more than 100 metres on his birthday to raise money for the NHS.
Bill Smith tackled the challenge in a pool at the Briary Court retirement facility in Cowes, surpassing his initial 100m target with a 136m swim and raising over £1,300 for NHS Charities Together.
The retired chef, who has lived on the Isle of Wight all his life, has been an avid swimmer since he was five and has a dip in the pool every morning at 7am.
In April this year, a centenarian fundraiser led a global walking challenge while fasting during the Islamic holy month of Ramadan. Dabirul Islam Choudhury, 101, was made an OBE after previous fundraising efforts raised more than £420,000 during lockdown.
Naturally, if we all could stay as healthy as these life-loving OAPs, most of us would love to make the century - and beyond. So what's the secret of healthy longevity?
Read more: Simple Ways to Live to 100, Say Experts
According to Margaret Warburton, 103, who lives at a care home in Essex, it's 'stay single'. Her words echoed those of Jessie Gallan who turned 109 in 2015 and advised interviewers that the secret was 'staying away from men. They’re just more trouble than they’re worth.'
Her fellow New Yorker Helen “Happy” Reichert, when still a New York university professor, aged 108, said that she hated salads, vegetables and getting up early. She preferred rare hamburgers, chocolate, cocktails and 'enjoying the nightlife'. She died in 2011, aged 109.
Others who have spoken out to local interviewers include Beryl Netto from New York, who insisted that eating puréed prunes and exercising every day kept her young. She stretched for half an hour before bed each night, aged 99.
Centenarian British ballet teacher Henry Danton said that taking care of his body was the key to his age.“It’s not amazing, you have to take care of yourself,” Danton told Today. “This body is the only thing you’ve got. You’ve been given this wonderful instrument, you have to look after it.”
By contrast, Mary Francis Carruba, who was 99 in 2015, believed that the secret was staying still.
“I was always a lazy bird,” she explained. “That’s the secret to living longer — be lazy.”
Famously, Frenchwoman Jeanne Calment who allegedly lived to be 122 (though some have questioned this number) ate more than 2 pounds of chocolate a week and smoked until she was 117 - though she did ride a bicycle until she was 100.
Read more: What People Who Live to 100 Eat Every Day
Last week, Julie Bush of Hampstead turned 100 and her granddaughter attributed her age to “whisky, walking, bananas and fighting fascism, not necessarily in that order.”
Few, however, are as impressive as Virginia Trapper, from Maine. She's 101 and still works on a lobster boat with her 78 year old son three days a week, waking for a three am shift. It's a job she's been doing since she was 8 years old - before the great depression.
She told a local news channel, "the doctor said to me, 'What are you out there lobstering for?' And I said, 'Because I want to'."
Watch: Guard of honour for D-Day veteran aged 101 who broke tandem skydive world record
Scientists have long been fascinated by what promotes a long life. The longest-lived communities are found in the Mediterranean, and in Japan, home to an astonishing 86,000 centenarians.
A new study from University of Western Australia has also looked at the factors influencing long life in men, led by Professor Leon Flicker who said: “Ageing well is the ‘new frontier’ in health. The concept is for people not only to live as long as possible, but also free from illness and engaged in life’s activities. It is something to which we are all looking forward."
According to a further study published in Nature Magazine, researchers have now discovered that centenarians have microbiomes with species producing unique bile acids, which may stave off illness.
"These bacteria might contribute to longer lifespans by providing colonisation resistance against (certain) positive pathogens and contributing to maintenance of gut homeostasis (a stable equilibrium),” said study leader Kenya Honda.
More research needs to be done on whether the link is genetic, dietary, both or neither.
Meanwhile, Iris Apfel has just signed up to a new campaign with a spectacles manufacturer, Zenni.
“I want to stay alive,” Apfel recently told The Wall Street Journal. “If I stopped working, I’d be gone.”
She has also commented: "Just because you are older doesn’t mean you have to stop living or working or roll up into a ball and wait until you pass on.”
Never a truer word - particularly for the new breed of active centenarians inspiring the rest of us.
Watch: 3 centenarians celebrate birthdays together in New York