it's called the lindisfarne gospels, and it's a 1,300 year old milestone in christianity's spread to the english-speaking world. fred de sam lazaro reports from the north of england. >> reporter: the large cathedral towers over the small city of durham, but durham cathedral's historical imprint is far wider. the foundation of christianity on the british isles was profoundly shaped by events, people, and relics connected to this 1100-year-old structure, including one relic that's come home to visit from safekeeping in the british library in london -- a book that is 1,300 years old. >> this is a book that has been dragged around the north of england on a cart, fleeing from the vikings, and the fact that it is still in near perfect condition shows how highly valued it was over the centuries, that people did look after it as well as they could. >> reporter: and to keep protecting it, professor richard gameson says visitors to the exhibit get to see just one open page of the lindisfarne gospels, the illumination of st. john that precedes his gospel. the space is kept cool and gently lit.