Four volunteer researchers have spent a year searching through the 35,000 books and files held in the library and archives of the Flemish abbey, first founded in 1128 by Saint Norbert of Xanten, and they cannot find the original recipe.

The monks last produced their dark brew in 1797, at which point the French Revolution shattered the monks’ communal life and their abbey’s walls.

They reinstated their home on the same site, in the province of Flemish Brabant, six miles (10km) north of Brussels, shortly afterwards, but the monks did not brew again.

In 1958, they came to a deal for the Belgian Maes brewery to use their brand, and today the beer is produced by the Alken-Maes brewery for Belgian drinkers and by a Carlsberg-owned brewery in Strasbourg for foreign markets.

The abbey’s subprior, Karel Stautemas, said: “It is an old dream to start again. Four men have been looking for that document for a year …

“Every day we get visitors who ask where the brewery is. And if you come from abroad, they do not understand that we do not brew beer. This is how the idea of re-establishing that tradition came to fruition.”

Stautemas said the abbey had received the support of Alken-Maes and Carlsberg for a micro-brewery “in the same place as where the brewery stood here until 1797”.

“Because we know the location, we have already found it in our archives,” he said. “We also have documents showing that the fathers then bought barley from local farmers. We even know all the ingredients. The only thing we do not know is how much we have to take from each. The composition is unavailable for now.”

Stautemas said he was still hopeful that the team of researchers would be successful in time. “They are not even halfway through [the records],” he told the Belgian newspaper Het Nieuwsblad.

“It is not such an easy job either, because those texts are in Old Dutch. But there is good hope that the recipe will turn up. And then there is the question: do we still like that medieval beer today?”

He added: “If everything goes as we hope and if we find the recipe quickly, we will drink our new Grimbergen at the New Year’s reception in 2020.

“The other types will also continue to exist. We can’t handle mass production. It will be a nice addition to the existing offer. And from then on, we will be able to show and offer the visitors something from the house.”

The Norbertine monks of Grimbergen use the phoenix as their symbol, in reflection of the abbey’s perpetual rebirth, and the motto “Ardet nec consumitur” (burned but not destroyed).

Daniel Boffey in Brussels