The murder of St Thomas Becket 850 years ago was a “John F Kennedy moment” that remains relevant in an age of Brexit, the Archbishop of Canterbury will say on Wednesday.

Becket was cut down by knights loyal to King Henry II on December 29 1170, in an assassination that shook medieval England.

But despite the passing of the centuries, his killing inside Canterbury Cathedral remains a shocking event.

Speaking later on Wednesday at an online preview of the British Museum’s new exhibition on Becket’s life, death and legacy, current Archbishop of Canterbury Justin Welby is to describe the saint as “fascinating, admirable, inspiring but also, entirely human”.

In a pre-recorded speech, Mr Welby will argue that his predecessor is “in many ways a relevant character for today” despite his death 850 years ago.

Parts of the archbishop’s address were shared exclusively with the PA news agency ahead of the event.

He adds: “He’s relevant because he speaks into a world which is struggling to cope with issues of the power of faith, the power of politics, and the power of faith and politics intermixed.

“His death at a time when intuitively we might have thought, in the middle of the Middle Ages, the death of an archbishop in the north-west corner of Europe could not attract much attention.

“His death caused outrage.

“It was in many ways a John F Kennedy moment, or a Dr Martin Luther King moment of its time.”

Mr Welby will speak at the virtual evening launch of the Thomas Becket: Murder And The Making Of A Saint exhibition for British Museum supporters on Wednesday evening.

The exhibition, which opens to the public on May 20, tells the story of Becket’s life through more than 100 objects, including a complete stained-glass window on loan from Canterbury Cathedral.

The window was made shortly after the saint’s death to depict his miracles, including a story of Becket curing leprosy.

During preparations for the exhibition, experts discovered that the stained-glass pieces had been assembled in the wrong order for hundreds of years.

Mr Welby will also speak about Becket’s enduring relevance when it comes to discussions of authority and identity in Europe.

He adds: “Becket therefore stood for something.

“Church versus state but he also seemed to be caught up in something, in a bigger argument about how nations are formed.

“About who is the ultimate authority, about where authority comes from, and about identity.

“Was Christendom the identity of Europe or was your belonging to a particular realm or empire in Europe your identity?

“Was there no such thing as a European identity?

“That may ring a few bells.”

Thomas Becket: Murder And The Making Of A Saint runs from May 20 to August 22 2021 in the Joseph Hotung Great Court Gallery at the British Museum.