New technology is being used at Beverley Minster to protect the 800-year-old building after a spate of lead thefts from churches in Yorkshire.
The minster is regarded as one of Europe's finest Gothic buildings
Workers have been on the minster roof marking lead with Smartwater - an invisible liquid containing a unique code - to deter thieves.
Lead has been stolen from the minster's parish hall and workman's yard.
John English, surveyor to the minster, said: "Such thefts are a sacrilege and rob us of our heritage."
Beverley Minster's maintenance joiner Steve Everett, who has marked out the key areas, is also putting up notices warning that the Smartwater is in place.
"Experience has shown that when criminals know there is a bigger chance of capture and conviction they will not take the risk," he said.
Mr English said: "Because of its size and location the minster is not so vulnerable as an isolated country church.
"Its height and the age of the structure also makes it hazardous to climb without special equipment and adequate precautions.
"But we have to protect it and the minster fund against more than financial loss."
Ecclesiastical insurers covering most of England's churches are encouraging the use of Smartwater after paying out more than £12m in recent months for lead and other thefts.
The marker remains detectable on skin and hair for weeks.
It remains on clothing indefinitely and also on stolen metals such as lead and copper even after they have been melted down.