Ice reveals mysteries behind medieval murder

Assassinated: Thomas Becket was beheaded in Canterbury Cathedral on 29 December 1170. © Getty

Is our history written in the air? Scientists have dug up evidence in the Swiss Alps that shows how the death of an archbishop in the 12th Century led to a drop in medieval air pollution.

Breaking news! Thomas Becket, the Archbishop of Canterbury, has been brutally murdered in his cathedral by four knights acting on behalf of the king of England.

This was the gruesome story that shocked medieval Europe 850 years ago. The Pope excommunicated the king, Henry II, and made Thomas Becket a saint. Appalled by what had been done in his name, the king did penance and walked barefoot to Canterbury, his monks whipping him as he went.

And now, a new discovery in the Colle Gnifetti glacier in the Swiss-Italian Alps sheds new light on the full impact of this political assassination.

Scientists have used highly sensitive lasers to examine tiny slices of ice that froze during the reign of Henry II. Trapped there is a record of the air pollution in Europe during the middle ages.

His death horrified Europe and plunged England into a political and economic crisis. Taxes went unpaid; the mines fell silent. And the air cleared above the Colle Gnifetti glacier.

Ten years later, King Henry was repairing his damaged reputation with the church by paying for the construction of monastic buildings, all needing lead for their roofs and stained glass windows.

Sure enough, the ice record shows lead pollution soared during those years.

So, is our history written in the ice and in the air?

Silent witness

Some say, yes, history is everywhere – if we know where to look. Frozen in the ice is the trace of 12th-Century air that can tell a story of murder, religion, and the rise and fall of kings.

Others are less sure. This is just one clue, one piece of evidence, that forms part of a bigger narrative. We can only make sense of the traces of lead in the glacier because of the rich historical records from the period.

You Decide

  1. Who do you think was to blame for the death of Thomas Becket?


  1. Use the expert links to research the events around the murder of Thomas Becket. On paper, create a newspaper front page with Becket’s murder as the main story, with an attention-grabbing headline and picture. Write the news story, including key events and interviews with witnesses and important people.

Some People Say...

“A historian is often only a journalist facing backwards.”

Karl Kraus (1874-1936), Austrian writer and journalist

What do you think?

Q & A

What do we know?
History is much more than a list of past events. It requires detective work to piece together clues and build theories of what happened and why. Traditionally, historians have looked at documents written at the time. But archaeologists can fill in gaps with material evidence, like the lead deposits in the Swiss glacier.
What do we not know?
No matter how much evidence we have, we can never be absolutely certain about historical events. Without a time machine to go back and check the facts, we can only interpret the clues and signs that have survived. Historical accounts can be unreliable, but so can deposits of lead pollution frozen in ice. Some scientists think the pollution came from German mines and not English ones, or that movement in the snow and ice makes them of no practical use.

Word Watch

Thomas Becket
He was a friend of Henry II who made him Archbishop to increase his power over the church. However, Becket defended the church and fell out with the king. In an angry outburst, the king famously said, “Will no one rid me of this turbulent priest?” Hearing the king, four of his knights rode off and did just that.
A very serious medieval punishment. It meant Henry II no longer had the support of the church and had no authority to be king. In the religious world of 12th-Century Europe, he could expect to go to hell when he died.
Henry II
King of England from 1154 to 1189.
Punishment inflicted on oneself as an expression of regret and repentance.
A large dense body of ice that builds up over many centuries.
Excavations (dug-up areas) in the earth for extracting coal, gold, tin, or other minerals.
Monastic buildings
Monasteries were at the centre of medieval life. They were vast complexes of churches, hospitals, schools, and manufacturing buildings.
A chemical element with the symbol Pb. It is a heavy metal that is denser than most common materials. When freshly cut, lead is silvery with a hint of blue; it goes grey when exposed to air.
Stained glass windows
Windows of small pieces of coloured glass arranged to form patterns or pictures, traditionally held together by strips of lead.

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