The bronze statue of the man in 18th-century clothing gazes into the distance. The statue stands in the US capital, Washington, and is a likeness of Thomas Jefferson. His likeness can also be found carved into the rocks of Mount Rushmore in South Dakota, alongside those of three other US presidents, George Washington, Abraham Lincoln and Theodore Roosevelt.

As the author of the US's Declaration of Independence, Jefferson is well known as one of the founding fathers of the country. Jefferson was a lawyer, plantation owner and politician. He served as the first secretary of state of the young republic, as its second vice president and then as its third president. His term as president is remembered for what is known as the Louisiana Purchase, the acquisition of the territory of Louisiana from the French. By buying this vast territory, the young nation almost doubled in size.

The Jefferson memorial in WashingtonImage: Alexander Farnsworth/picture alliance

But like almost every celebrated historical icon, Jefferson also had a dark side, one that has really only been openly discussed for the last few decades.

This darker aspect of his biography is closely linked to Thaddeus Kosciuszko, a military engineer from Poland, who became one of the most important figures of the American war against the British. Many streets, squares and bridges in the US bear his name today – although the spellings of his name are not always the same, with some calling him Tadeusz and others leaving the "z" out of his surname.