In that capacity he participated in numerous negotiations with foreign delegations in Warsaw. In August 1945 he was a member of the Polish Delegation, as its interpreter, to the UNRRA Conference held in London. In the autumn of that year he was appointed counsellor to the embassy in the Hague, but that appointment was cancelled for political reasons, due to his origins and his alleged Home Army past. He returned to Kraków to complete his studies – firstly at the Academy of Economics, obtaining his degree in 1947 and then in the Faculty of History of Art of the Jagiellonian University, gaining his Master of Arts degree in March 1950. At the same time, he was involved in student activities and was the founder of the "Club of the Logophagoi", (Klub Logofagów), a debating society which comprised many prominent students and young scholars – some eminent politicians and scholars were to emerge from its ranks. The club was also the prototype for later clubs of the Catholic intelligentsia, which was preparing for the fall of Communism. Having completed his studies, he was almost immediately appointed lecturer at the Institute of History of Art. Work on his doctoral thesis was interrupted by his arrest on 22 October 1950. Transported immediately to Warsaw in connection with the staged "British Embassy" Show trial and after lengthy interrogations, he was sentenced to ten years in prison in February 1952 for allegedly helping British and Vatican spies, as well as for extending his underground activities beyond the official date for disclosure, which, in any case, would probably have led to an earlier arrest. He spent five years and four months in prison in difficult conditions – firstly on remand in the cellars of the Ministry of Public Security in Koszykowa Street, and later in the infamous Mokotów Prison, both in Warsaw, and finally – after sentencing – in the prisons of Rawicz and Wronki. In the latter two he actively organised spiritual help for his fellow prisoners. Having got himself work in the prison hospital, he was instrumental in forging documents enabling the early release of a very large number of political prisoners. He himself was released on 6 March 1956 less than midway through his sentence. He was later cleared of all charges, probably in exchange for becoming an informer, especially on foreign trips. Returning to Kraków, he took up his doctoral thesis and also worked on other research projects. He was a consultant at the Wawel Castle Museum and also a curator at the Castle Museum in Łańcut.