As competitors turned out in all their finery for the first day of Norfolk's newest equestrian event yesterday, one rider took part in some impromptu undressage, with little more than her jewels and her trusty steed for company.

As competitors turned out in all their finery for the first day of Norfolk's newest equestrian event yesterday, one rider took part in some impromptu undressage, with little more than her jewels and her trusty steed for company.

First time model Caroline Bullard, 23, a member of the well-known equestrian family from Gressenhall, was the first in a procession of country types who will are baring all over the next few days for a charity calendar.

While Houghton International Horse Trials got under way on one side of the imposing stately home of the Marquess of Cholmondeley, the odd passer-by and dog walker were greeted on the other side with the sight of Caroline wearing not much more than her top hat and riding boots.

And while the legendary Lady Godiva had her hair to cover her charms as she rode through the streets of Coventry to show solidarity with down-trodden country people back in the Middle Ages, Norfolk's modern-day answer came draped with £750,000-worth of diamonds.

“That necklace alone is £350,000, it's champagne diamonds. Add the earrings, bracelet and hair band and you're talking three quarters of a million,” said Edward Wain, boss of King's Lynn-based Francis Wain jewellers.

“The necklace is actually already sold, I can't disclose to whom of course, but they've very kindly loaned it to us.”

King Lift, a seven-year-old gelding, kept his eyes politely to the fore and behaved impeccably, as stylist Beth Jex adjusted the sparklers to catch the sun. “We've brought a mixture of jewellery to try out to see what works,” she said.

Mr Wain said the calendar was being produced for the Brian Cross Memorial Trust, a new cancer charity being set up in memory of former West Norfolk Hunt master Brian Cross, who died last year from a brain haemorrhage at the age of 62.

Caroline's mother, Tania Bullard, said: “He was my next-door neighbour for 15 years - he was a wonderful neighbour and friend.”

Mrs Bullard said another 27 models had agreed to pose for the calendar at a secret location somewhere in Norfolk this weekend.

“They'll all be posing saucily in some way,” she said. “They're all people who are keen on the countryside or have had something to do with cancer, perhaps their mother has had breast cancer or something like that.”

One passer-by who stumbled across yesterday's shoot observed: “Cor - you see everything in Norfolk don't you.” Another quipped: “It all happens at Houghton Hall.”

Mr Wain said: “Brian Cross would have thoroughly approved of this sort of thing you know. Except he'd probably have been here telling everyone what to do.”

Mr Cross was a former Dereham mayor who founded the Big Fry chain of fish and chip shops, after a spell as a concert promoter in which he brought both Rod Stewart and Jimi Hendrix to Norfolk.

Caroline and King Lift will be joined in the finished product by both male and female models, including a blacksmith, an angler and greyhound breeder. “It's the first time I've done it properly with such fantastic jewellery and such an amazing setting,” said Caroline, who is in her final year at the Royal Veterinary College, in London, before joining an equine practice. “It's all for a good cause - I wouldn't get my kit off otherwise.”

Houghton International Horse Trials continue today with dressage (fully-clothed…), cross country tomorrow and show-jumping on Sunday.

Gates open at 9am each day; tickets today cost £3 adults, children free, while tickets tomorrow and Sunday are £6 adults, £3 children. Parking is free and dogs on leads are welcome. For more information go to www.houghtoninternational.co.uk