For ten years Oxford professor Martin Biddle has been quietly unlocking the secrets of what for millions is the holiest ground on Earth.

Now he believes he is close to answering the question that has obsessed Christians for centuries: Where was Jesus Christ buried?

Millions of pilgrims visit the Holy Sepulchre Church in Jerusalem, which for 1,700 years has been recognised as Christ's burial place.

But its special place in the story of Christianity has always been more to do with faith than scientific knowledge - until now.

For Prof Biddle has established that the 19th century marble structure withholds secrets, scarcely dreamed of even by the many religious communities who share the world's most famous church.

Experts have long thought that nothing significant remained of the burial cave, where tradition has it that Christ's body was laid after his crucifixion.

But Prof Biddle, a leading medieval archaeologist of Hertford College, is now convinced that part of the original rock-cut tomb remains hidden deep within the existing structure

He said: "People have said, and continue to say, that there is little to be found. But we have done a thorough examination and we are reasonably sure that some parts of the original rock cut tomb survives to about the height of a man.

"There has always been a possibility that this was the authentic tomb of Christ. Now we think that it is a probability."

Prof Biddle and his wife, the eminent Danish archaeologist Birthe Kjolbye-Biddle, were first asked to carry out the most detailed investigation of the tomb ever undertaken back in 1986.

While they always hoped that the project would lead to new discoveries about the holiest shrine in Christendom, their involvement stemmed from a more pressing priority.

The present shrine above the tomb, dating from 1808, is falling down, with the whole monument held up by a steel cradle put up by the British in 1934.

A definitive archaeological record was wanted in advance of restoration.

Prof Biddle, of Banbury Road, certainly made the most of his unique opportunity.

He was joined by scientists from London City University who provided detailed measurements, using highly accurate laser and computer equipment to map the history of the shrine. The Oxford archaeologist said: "The structures on top of the tomb are like the skins of an onion, one built outside the other. "I do not think there is any doubt that there is a rock cut tomb inside, built at the time of Christ.

"We have been able to make this deduction using a combination of precise survey techniques, detailed observation and written accounts of the 16th century.

"The question is, is it the tomb where the body of Christ was laid after the crucifixion? Is it authentic? I think the answer has to be yes."

He said that the tomb was consistent with the one described in the Gospels and had been recognised as authentic since the time of Constantine the Great. And now crucially Prof Biddle has made use of an early guide to Bible place names produced by Bishop Eusebius, of Caesarea, dating from 290AD, which record Golgotha as a place still to be pointed out in Jerusalem.

The vast church of the Holy Sepulchre is also thought to encompass the site of the crucifixion.

Prof Biddle, who is producing a book about his discoveries in February, hopes to help unravel more of the mysteries of the tomb when the crumbling shrine is rebuilt.

The various church communities who jealously guard their positions as guardians of the church are now determined to have the tomb restored in time for the Millennium celebrations.

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