Diplomatic relations between Britain and Italy predate both Britain and Italy's unification, with diplomatic exchanges between the Papal States and England growing particularly heated during the investiture disputes between kings William and John and their respective archbishops of Canterbury Anselm and Langton.
The latter feud ended with John's excommunication being lifted in exchange for swearing his fealty to the papacy.

Later, the Court of St. James hosted ambassadors from various states of the Italian peninsula, including those of the Kingdom of Sicily and Piedmont's Count Perron.

The British government gave moral and diplomatic support to the "Risorgimento" (Unification of Italy) and the creation of the modern Italian state against considerable international opposition.
 The famed hero of unification, Giuseppe Garibaldi was widely celebrated in Britain, with a peak in 1861.
Diplomatic relations between Britain and Italy predate both Britain and Italy's unification, with diplomatic exchanges between the Papal States and England growing particularly heated during the investiture disputes between kings William and John and their respective archbishops of Canterbury Anselm and Langton. The latter feud ended with John's excommunication being lifted in exchange for swearing his fealty to the papacy. 
Later, the Court of St. James hosted ambassadors from various states of the Italian peninsula, including those of the Kingdom of Sicily and Piedmont's Count Perron.
The British government gave moral and diplomatic support to the "Risorgimento" (Unification of Italy) and the creation of the modern Italian state against considerable international opposition.  The famed hero of unification, Giuseppe Garibaldi was widely celebrated in Britain, with a peak in 1861.
Italy–United Kingdom relations