Well known for his histories of Norman Sicily, Venice, the Byzantine Empire and the Mediterranean, John Julius Norwich has now turned his attention to the oldest continuing institution in the world, tracing the papal line down the centuries from St Peter himself - traditionally (though by no means historically) the first pope - to the present day with lively investigations into the anti-Semitism of the contemptible Pius XII, and the possible murder of John Paul I.
Of the 280-odd holders of the supreme office, some have unques-tionably been saints; others have wallowed in unspeakable iniquity.
John Julius Norwich continues his history of the papacy today with a period of immense political turmoil.
In 1152 Frederick Barbarossa became King of the Romans - determined to take his place as successor to the great Charlemagne.
At the same time the Norman King William of Sicily harboured expansionist ambitions and in Rome the threat of civil war simmered.
In the middle stood the only English pope in the Papacy's history: Nicholas Breakspear, Hadrian IV.
Producer: David Roper
A Heavy Entertainment production for BBC Radio 4.
Nicholas Breakspear was the only English pope - elected into tumultuous 12th-century Rome.