William Harcourt-Cooze, a self-styled Willy Wonka, is launching what is thought to be the strongest chocolate on sale in any UK supermarket.

With 100% cacao content, the chocolate is believed to be more suited for recipes than for eating, and is set to be rolled-out in Waitrose stores around the UK with immediate effect.

Harcourt-Cooze 's unique Venezuelan Black was produced after a life long quest to find the "perfect chocolate", which was followed by Channel 4 in the documentary Willie's Wonky Chocolate Factory.

"Many people who knew me thought this was a madcap scheme, but for me it's a passion and I've never been more serious about anything in my life," said Harcourt-Cooze. "I've seen my bank manager more often than my wife in the last couple of years. But seeing the results of my labour on the supermarket shelves will be like a dream come true."

Eleven years ago Harcourt-Cooze purchased land in Venezuela and planted 10,000 cacao trees at the Hacienda El Tesoro. Soon afterwards he set up a small chocolate factory in Devon.

"Chocolate is Willie's life and his passion shows in the high quality of Venezuelan Black", said Waitrose home baking buyer, Christopher Moore. "A chocolate with 100% cacao content is something we haven't offered our customers before. The strongest we currently offer is 85%."

Waitrose will be stocking all three cacao bars from Venezuelan Black.