World's most famous 'unseen' diamond

The room was dimly lit. Armed guards stood at both entrances and enormous ironclad doors were slid shut to seal the gallery.

Nobody spoke above a whisper as we waited for the first glimpse in half a century of one of the world's most extraordinary gems.

The Wittelsbach-Graff Diamond was last seen in public at the 1958 World Exhibition in Brussels. After that, it disappeared and its whereabouts remained a mystery until Laurence Graff, a billionaire diamond dealer, bought it at auction in 2008, appending his surname.

He and his son Francois were in the gallery of the Smithsonian's National Museum of Natural History in Washington DC as the blue stone, was brought up from a secret vault and finally revealed.

Flawless beauty

"I've been privileged over the years to own some of the world's most important and famous diamonds, but I would say that the Wittelsbach-Graff is the most valuable and the most beautiful," he said.

Under ultraviolet light, the diamond has an orange hue

Sitting unadorned on a silken white cloth, it glittered grey and blue in the low light. Classed as "internally flawless" it is said to have exceptional colour and becomes intense orange when viewed under ultraviolet light.

"When I saw this stone, I knew it was a stone we had to have," said Laurence Graff. "I had the opportunity to examine and value it in my own offices, and I came to the conclusion it was one of the rarest stones I'd ever seen."

'True perfection'

Initially valued at around $15m, Mr Graff paid more than $25m. In a controversial move he had it re-cut and polished, reducing it from 35.5 carats to little over 31 carats. Critics say the act compromised the historical integrity of the stone, but Mr Graff disagrees.

"I decided that to create beauty, or acts of beauty, is not a sin. All we did was remove the blemishes and now it's true perfection. It's the most wonderful diamond to hold in your hand. It's got the most incredible feel to it - a magical feel. We have managed to bring out the true colour of the stone without changing the faceting or the shape.

"The true rarity of the diamond, whatever its history, is the diamond itself. The history will continue. Every diamond that was ever mined, every diamond that was ever polished and cut, is still with us. Who knows the story that this stone will tell in a thousand years time. I'm sure it will gather very romantic stories, mysterious stories, intriguing stories, but at the end of the day the true beauty of the stone will remain. That will always be the best story."

Francois Graff compared the decision to restoring a priceless painting. "If you discovered a Leonardo da Vinci with a tear in it and covered in mud, you would want to repair it. We have similarly cleaned up the diamond and repaired damage caused over the years."

Distant cousins

The Wittelsbach-Graff Diamond originated in India. In 1664, Philip IV of Spain gave it to his daughter, the Infanta Margarita Teresa to celebrate her engagement to Emperor Leopold of Austria.

In 1772, it acquired its name by passing to the Wittelsbach family of the House of Bavaria. After World War I, Bavaria became a republic and the Crown Jewels, including the diamond were sold.

For the next hundred years it was rarely seen in public.

"It's probably the most famous diamond the world has never seen," said Jeffrey Post, curator of the Smithsonian National Gem Collection. "It's always been lurking out there - but we've never seen it."

The Wittelsbach-Graff was secretly transported to the museum in the dead of night, a week before it was due to go on display.

The Hope and the Wittelsbach are believed to be in a class by themselves

Mr Post and some of the nation's leading diamond experts locked themselves in the vault to spend the time examining it and comparing it to the legendary Hope - the world's largest blue diamond at 45.52 carats - which is the star of the National Gem Collection.

It was thought that the two may once have been part of the same crystal, but tests proved negative. Although they share significant similarities and come from the same place, the Hope and the Wittelsbach-Graff are more like distant cousins than siblings.

"We had this confluence of history with two of the world's great diamonds," said Mr Post, "and an unparalleled opportunity to examine them. Diamonds have been mined for hundreds of years but in all that time these two stand in a class by themselves unlike any other diamond found."

Diamonds are typically formed about 100 miles underground and are billions of years old. They can tell scientists much about the history of the planet.

The Wittelsbach-Graff will be displayed alongside the Hope at the Smithsonian's National Museum of Natural History until August. After that, its future is uncertain.

Laurence Graff says it may move to London's Natural History Museum - but it could also be sold. If that happens, it could disappear for another hundred years.

The ice-cream parlour with 860 different flavours

You might imagine that the shop selling the largest number of ice-cream flavours in the world would be in Italy or perhaps the US, but in fact it is in the Venezuelan city of Merida, as Will Grant discovered.

After looking in the windows of a couple of ice-cream parlours but finding nothing more exciting inside than strawberry and vanilla, we eventually find Coromoto, opposite a church.

The neon sign outside, with the words "Guinness Book of Records" written in pink, is an instant give-away but, once through the doors, it becomes even clearer that this is the place.

At first glance, the counters of brightly coloured ice cream look perfectly ordinary.

Close up, the flavours are anything but.

The selection includes chilli, tomato, gherkin, onion, mushrooms in wine, garlic, and cream of crab.

Coromoto was set up in 1980 by a Portuguese immigrant, Manuel da Silva Oliveira.

The owner does not come in much any more and has left the running of the place to Jose Ramirez.

Seasonal changes

Jose is exactly what an ice-cream parlour manager should look like.

A friendly man in his 40s, his white and purple shirt is spotlessly clean, and his black moustache is perfectly groomed.

"Mr Oliveira was tired of working for the big ice-cream companies," Jose says, "and decided that he could make more interesting flavours on his own."

The first attempt was avocado.

"It's a tough one to get right because avocados are so rich," says Jose.

"Mr Oliveira wasted around 50kg of ice cream trying to perfect it."

Coromoto sells about 60 flavours on any given day, but changes the flavours according to the seasons.

On one wall, a list of its specialities is made out of engraved wooden slats.

Besides the standard options like chocolate and rum-and-raisin, there are plenty of exotic fruits: guava, papaya, mango and passion fruit.

There are several vile-sounding flavours among the 860 as well: eggs, macaroni cheese and sardines-in-brandy being a few of the more bizarre examples.

And there are a lot of oddly named ones too like British Airways, Andean Kisses and I'm Sorry, Darling.

One of them, Viagra Hope, is bright blue like the pills.

I have to ask what is in it, and am relieved to hear it is all natural: honey and pollen.

"Different people like different things," said the shop's manager.

"Personally I'm a fan of the fruit flavours but many customers prefer the alcoholic choices like Cointreau, cognac or vodka-and-pineapple.

"Of course, being Venezuela, there are plenty made with rum."

In the back room

Ushered behind the front desk, I get the chance to glimpse what most visitors to Coromoto never see: the ice cream being made.

The house special is made with several flavours including beef and cheese

As we walk behind the scenes, I imagine scenes of an ice-cream version of Willy Wonka's Chocolate Factory, complete with a mad inventor pouring strange solutions into test tubes.

However, a bit disappointingly, I am led into an airless room where two vast ice-cream mixers are whirring away.

On one of the machines, a big tub of raisins is waiting to be added to the concoction inside.

In the other, a vanilla-coloured mixture is being turned but - as I suspected - it is not vanilla.

"Es cafe," says the girl keeping an eye on the machines - coffee flavour.

Now it is my time to try a few.

'Muy picante'

"What is the house special?" I ask Jose.

He chuckles and says "pabellon criollo" - a traditional Venezuelan meal of beef, rice, plantain, cheese and black beans, which Coromoto has replicated in ice cream.

Jose fixes me a small scoop of each flavour - and yes, they do beef-flavoured ice cream in Coromoto - topping it off with a half-scoop of chilli flavour.

"Muy picante," he warns me, but I foolishly nod... I'm sure it's not that hot... and gulp it down in one.

Once my eyes have stopped watering and I have got my breath back, I manage a smile at Jose, who is laughing and saying, "I told you so!"

Clearly Coromoto's flavours live up to their names.

To put out the fire on my tongue, I go for the plantain flavour which is incredibly realistic. As is the cheese, which I would not at all recommend.

Perhaps some things, like cheddar, should not be made into ice cream.

Finally the beef. Despite my misgivings, it is rich, sweet and meaty. I can't quite believe it, but I seem to actually like beef-flavoured ice cream.

Back on the shop floor, the customers are enjoying their choices on what is a stiflingly hot day.

"I chose a scoop of avocado and a scoop of sweetcorn," says Marjorie Castillo, who lives in Caracas.

"It's amazing. The avocado tastes just like avocado and the sweetcorn like sweetcorn."

Her 14-year-old niece, Marvery, concurs. "It's exotic, divine," she says.

"You've only got 858 flavours still to go," I tell her.

"I know," she says, giggling into her ice-cold treat. "But I'm sure I can do it. One flavour at a time!"