But they did not know where the object was, until they discovered the stone construction after recently stumbling across the remains of an annex of his house in Wittenberg, south-west of Berlin, during plans to plant a garden. "This is a great find," said Stefan Rhein, the director of the Luther Memorial Foundation.

"This is where the birth of the Reformation took place." He said that until now little attention had been paid to anything "three-dimensional and human" in the writing of the theses. "Luther said himself that he made his reformatory discovery in cloaca [Latin for "in the sewer"]. We just had no idea where this sewer was. Now it's clear what the reformer meant."

What makes the find even more fitting is that at the time faecal language was often used to denigrate the devil, such as "I shit on the devil" or "I break wind on the devil". Professor Rhein said: "It was not a very polite time. And in keeping with this, neither was Luther very polite." The 450-year-old toilet, which was very advanced for its time, is made out of stone blocks and, unusually, has a 30-square-centimetre seat with a hole. Underneath is a cesspit attached to a primitive drain.

Other interesting parts of the house remains include a vaulted ceiling, late Gothic sandstone door frames and what is left of a floor-heating system, which presumably gave Luther an added bit of comfort during the hours he spent in contemplation. Luther, who was professor of biblical theology at Wittenberg University, nailed his 95 theses to the church door at Wittenberg, attacking the corrupt trade in indulgences. The act led to his excommunication but he was protected by Frederick II of Saxony and was able to develop and spread his ideas. Professor Rhein said the foundation would stop at letting the annual 80,000 visitors to Wittenberg, who come in search of the spirit of Luther, from sitting on the toilet. "I would not sit on it. There's a point where you have to draw the line."

The Telegraph, London