Part of the Vatican's secret archive relating to the Inquisition, the Catholic Church's long battle against Protestant heresy, is to be opened to qualified historians for research purposes. David Willey reports from Rome:

The formal announcement of this small concession to professional historians will be made later this month by Cardinal Josef Ratzinger, who is in charge of the Vatican department known as the Congregation for the Doctrine of the Faith.

This department used to be known as the Holy Office, and four centuries ago it spearheaded the Catholic Church's attempts to combat the Protestant Reformation by trial, torture and even the burning to death of suspected heretics.

A meeting in Rome later this month of Italy's prestigious Academy of Letters and officials of the Vatican Archive will be the occasion for this announcement.

The Vatican jealously guards the secrecy of its historic archive, one of the richest and most complete collections in the world of European diplomatic papers and documents dating back to the Middle Ages.

Among its more curious items, the love letters of King Henry VIII of England, which were smuggled back to Rome by a Vatican spy, and some letters from Lucrezia Borgia to her father, Pope Alexander VI.

The Vatican is particularly sensitive to the publication of its contemporary archives and imposes an almost hundred-year ban on documents relating to papal elections.

The latest papal reign available for selective scrutiny by scholars is that of Pope Leo XIII, who died in 1903.