A little known Whitehall office responsible for ensuring that people celebrating their 100th birthday receive a card from the Queen has had to take on extra staff because of the dramatic increase in the number of centenarians.
The Department for Work and Pensions now has a seven-strong "Centenarian team" dedicated to keeping information on Britain's oldest citizens up to date after the number of people over the age of 100 jumped by 70 per cent in a decade.
New estimates published by the Office for National Statistics show that there are now almost 14,000 people over the age of 100 living in the UK, a five per cent rise in a single year.
Analysis of the figures also shows that there are still around 104,000 people born during the course of the First World War alive in Britain.
While medical advances are the main explanation for improvements in life expectancy, the study highlights how events almost a century ago are also still having a direct effect in shaping the UK's current elderly population.
The ONS said that the increase in the number of people over the age of 90 had gathered pace in recent years partly because there was a slump in the number of births during the First World War when soldiers were at the front followed by a baby boom when they returned.
The figures show that the number of people over 90 in the UK last year was 25 per cent higher than just four years earlier, partly reflecting how many more babies were born when the war ended.
Overall there are estimated to have been 527,240 people over the age of 90 living in the UK last year, accounting for almost one per cent of the entire population.
The UK has proportionally the seventh largest population of over 90s in the world, behind Japan and a small number of Scandinavian and Mediterranean countries.
Separate analysis by the ONS also shows that far from expecting to live to the traditional "three score years and 10", it is becoming the norm for people to live until they are 90.
The ONS said that the most common age for women to die last year was 89 – compared with 85 a decade earlier.
And the figures suggest 90 will soon be the most common female lifespan, with only marginally fewer women dying at 90 as at 89 last year.
Although the most common age at which men died last year was 86, up from just 81 a decade earlier.
The analysis shows that men are rapidly closing the life expectancy gap on women, a phenomenon attributed to changing lifestyles, such as the decline in smoking, and the shift away from heavy industry.
The ONS has upgraded its estimates of life expectancy from birth – the time a typical newborn baby would be expected to live if there were no improvements in mortality rates – to 82.7 years for girls and 78.9 for boys.
That means that male life expectancy in Britain is increasing by 6.3 hours a day and female life expectancy is gaining 4.6 hours a day.
Overall the figures show that the number of people over 100 has jumped 8,060 to 13,780 between 2003 and 2013.
The number of people aged over 105 almost doubled from 360 in 2003 to 710 in 2013.
As a result the DWP's centenarian team has recently expanded from just one official to seven members of staff.
Margaret Wilberforce-Eke, the department's Centenarian team leader, said: "We get to speak to some fascinating people with some amazing stories about their lives over the last century.
"We hear about people celebrating their big days with street parties, hot air balloon rides, trips of a lifetime abroad, and even a pool party.
"Playing a part in their celebrations is really rewarding and we look forward to helping thousands of people have a happy 100th birthday this year."
Iain Duncan Smith, the Work and Pensions Secretary, who also sends centenarians a card, said: "It is a privilege to send these cards and help the hundreds of people each year celebrate their special birthday.
"Our ageing society can only be a cause for celebration and our reforms to pensions are ensuring the system can stay strong as the number of people in Britain hitting 100 'not out' increases."
