Clemens Laby was born in Beuthen (today known as Bytom), a mining town near Kattowitz (today Katowice) in Upper Silesia. Towards the end of his time at senior school, around 1920, he worked as an intern at the "Oheimgrube" (today Wujek) coal mine. He then moved on to the Technical University (TU) of Berlin where he studied mine engineering, obtaining his degree in or before 1926. It is from the record of his registration at the TU that his birth date and birthplace can be ascertained. The outcome of the 1922 referendum had moved the Polish frontier close to Beuthen, and in 1926 Laby went to work for the Polish mining administration. After the Annexation of Western Poland by the German army Laby was transferred to Germany's national head office of the Combustible Fuels Industry, taking a senior management position in the Bituminous coal department based in Berlin. It was here that he met the jurist Karl Laurenz in 1945, while Laby was working as a safety expert with the "Mining Technical Inspectorate". Between 1946 and 1949 Laby was also working as personal assistant to the President of the National Administration (for what had become, in May 1945, the Soviet occupation zone). The National Administration was the forerunner to the in what became, in October 1949, the German Democratic Republic. According to testimony given by Laurenz at his trial in 1955, Laby had had to leave the National Administration in 1949 because he had had to relocate from East to West Berlin - something he had done only reluctantly.