It's perfect for sharing and at 10 pounds for one of these flasks, a specialty at British coffee house Caravan.

But there's a crisis brewing in the coffee industry that is threatening the supply of premium beans.

And that could leave customers with a bitter taste.

Jeffrey Young is from coffee consultants Allegra Strategies.

"It takes four years for a plant to come on tap, four, five years for a coffee tree to turn into something you can actually roast."

What we could see here is a chronic long-term shortage of supply.

A combination of drought in Brazil, the world's biggest coffee producer, farmers quitting for better-paid jobs in the city, climate change and the rise of artisan coffee shops and you have a recipe for disaster.

Steve Hall is Caravan's chief coffee buyer.

"If coffee production goes down, the the whole world is going to be screaming out for coffee, and we're going to have to look for other ways to get around this."

That means investment.

And could take years.

For now coffee lovers such as Lassi Jarvela are left facing higher prices.

"It would become more of like having a glass of wine that you just do once in a while as a luxury."

The taste for coffee is spreading.

China is opening the equivalent of four new coffee shops a day.

In Europe they've added 2,000 more in less than two years.

And last year the number of coffee shops in Britain surpassed 20,000.

Figures from the International Coffee Organization suggest overall coffee production is already lagging demand.

In 2014, 150 million bags were consumed, 7 million more than were produced.