They also survived the fire that ravaged through the church four years later. Conservationists previously believed that no windows had survived this.

An archeologist in 1987 suggested that the windows were older than believed because they had a different style.

Ian Freestone, professor of archaeology, materials and technology at UCL, said: “The Ancestors of Christ windows were in the conservator by chance, it was an excellent opportunity.

“It took about three years from developing the method, validating it, analysing them and then working out what it all meant.

“It slowly dawned on us as we were analysing that we were able to prove a theory made by a historian named Madeline Caviness back in the 1980s that this particular group of windows were made earlier and our results were completely consistent with that.

“It all fitted together really well. I am really happy, it is nice to have done something which is so obviously in the public eye and it was really satisfying.”

Léonie Seliger, the head of stained glass conservation at Canterbury Cathedral, told The Telegraph: “The windows are about 50 years older than previously thought and that is a very important step. 

“It takes us back into a realm where there are really only a handful of stained glass windows surviving in the world.”