Six of the original Calendar Girls have been attending a royal reception at Clarence House to celebrate their charity fundraising reaching £1 million.
Actresses appeared with WI members in a 2004 calendar
The group continued raising cash for the Leukaemia Research Fund long after their near-naked Women's Institute calendar became a phenomenal success and the subject of a hit film.
The success of North Yorkshire's Rylstone and District WI's 1999 calendar also launched a copycat craze which has become an established form of fundraising.
Tricia Stewart, who came up with the idea of a WI calendar which mingled jam and knitting with glimpses of flesh, said there had been around 200 copycat calendars last year alone.
"But it's great because they're all doing it for a good cause and they'd have raised money and they'll have had a brilliant, humorous, time doing it like we did," she said.
The death of Angela Baker's husband John had inspired the WI women to raise money. The calendar used items such as cakes and flowers to protect the women's modesty.
It now seems that no sooner discussion over a good cause begins than someone suggests a fundraising strip.
Ambulance crews, builders, chefs and gamekeepers have all embraced charity nudity, raising money for causes ranging from cancer to Christmas lights.
The trend has also become international, embracing an Australian women's football team as well as nude farmers in South Africa, who became local pin-ups.
Many calendars are one-off fundraisers, bought locally by people supporting familiar faces in unusual guises.
This was the case at Barsham, Suffolk, where local minister John Buchanan and parishioners defrocked to raise money for the 1,000 year-old Holy Trinity Church.
Rev Buchanan said the calendar was tasteful, with nothing "too risqué".
"I do a lot of grass cutting, so was pictured with a lawn mower - with the grass box strategically placed," he said.
He said the idea was presented at a church meeting and went ahead after the rector agreed.
"There was a little bit of argy bargy about it," he said.
"But people always take different views. There's precious little you can do without somebody going against it. But it wasn't a major row and any family has disagreements."
"Some people thought it was terrible having naked bodies round the church, but you don't have to look far in most churches before seeing a statue of a naked cherub or nude paintings."
He said the charity raised around £2,900 towards the church's upkeep.
For the minister there is little mystery as to why the calendar craze has taken off.
A chorister became a Heavenly Hunk for the month of May
"I just think people jump on the band wagon," he said. "You know they say it took one blue tit to pierce the top of the milk bottle to discover the cream, and every blue tit in the UK to follow it."
But as well as the one-off fund-raisers, other calendars have returned by popular demand.
The "Heavenly Hunks" calendar by Portsmouth Cathedral Choir, has gained an international following and been produced for three years running.
Andrew Cooper, who runs the calendar's website, said it had received massive support.
"The internet has given us access to a whole niche market," he said. "There is a global community interested in what we are doing and who want to also raise money for Macmillan Cancer Relief."
The calendar, which also raises money for Portsmouth Cathedral Choir Association, raised £6,000 for charity last year - double the previous year's amount.
Many charity calendars followed the Calender Girls' tongue-in cheek style and have been well-received.
But several have caused offence and been criticised for going beyond Britain's traditional postcard sauciness.
A row brewed at Manchester University in 2002 after a calendar of scantily-clad students was banned from campus shops.
Last year, the Magpie Appeal at the Royal Hampshire County Hospital, Winchester, felt poses by their own estate workers were too racy and would not accept the funds raised.
Antony Robbins, Head of Communications at the Charity Commission, praised charity calendars, but sounded a note of caution.
"It's all good clean fun and it's excellent that the WI was so successful in raising money and that there have been so many other initiatives," he said.
"But we would urge charities to be careful and to think hard about how they are going to use such calendars and these images and to make absolutely sure they will not damage the charity's reputation or embarrass or offend its supporters or themselves.
"There have also been a few rare cases where those taking part have found themselves in deep water when images have been posted on the internet. It may be something they regret in the cold light of day."
Meanwhile, as the charity trend looks set to continue, Calendar Girl Angela Baker said ahead of the royal reception it "was fantastic to know" that they had the idea first.