For centuries, he remained the central figure in the celebration that bears his name.

But in the new millennium that marks his birth, he seemingly has little more than a cameo role for millions of adults. The name on the lips of most children is Father Christmas, whose modern form is largely a creation of Coca-Cola.

Many features of the Christmas festivities are, of course, of pagan origin. Yet millions of people who annually indulge in an orgy of spending, feasting and drinking, also find themselves singing carols that exhort the name of Jesus Christ.

And in thousands of schools, doting parents watch their children in nativity plays, depicting the familiar story of the baby in a manger.

Bethehem: Centre stage now and then

The story of Christ's birth relies mainly on St Luke's Gospel, but theological and historical studies have questioned many of its details.

It is widely believed that Jesus, a Palestinian Jew, was born some weeks prior to 25 December, probably between the years 4 and 7 BC, and that his birthplace may not have been Bethlehem.

According to St Matthew, the wise men, or magi - meaning astronomers - were able to locate Jesus when "the star which they had seen in the east went before them, till it came and stood over where the young child was" (New King James Version).

Astronomers continue to speculate about an explanation for this extraordinary event.

Chandra Wickramasinghe, Professor of Applied Mathematics and Astronomy at Cardiff University, leans toward the possibility of a fireball comet, spinning in time with the Earth, and scattering small meteoroids which would perhaps have been immortalised by watching shepherds as a "host of angels".

Botticelli's The Virgin Adoring the Sleeping Christ-Child

And new research suggests that in November, 7 BC, there was a real astral event corresponding to St Matthew's account, with Jupiter and Saturn standing still together in the Western sky - and clearly visible above Bethlehem.

Few matters in the Bible are more contentious than the Virgin Birth.

The debate within the Churches is intense. The Roman Catholic church maintains that Mary was "ever-Virgin", while some Protestant churches teach that Jesus was conceived by Mary and the Holy Spirit and that she later had other children fathered by Joseph.

Vying for that number one spot

But if there is controversy about what the Bible says, there is next to nothing in the New Testament about the period between Jesus's childhood and the last three years of his life.

He spent the key part of his life as an itinerant teacher in Galilee and was executed around 30 AD by crucifixion, a painful and degrading form of death reserved for criminals.

And what reputedly happened after Jesus's death, the Resurrection, poses the biggest question of them all - was he the Son of God?

Whatever your beliefs, CS Lewis insisted that question could not be evaded. "You must make your choice", he wrote. "Either this man was, and is, the Son of God: or else a madman or something worse.

"But let us not come up with any patronising nonsense about His being a great human teacher. He has not left that open to us. He did not intend to."

Jesus has been the focus of more study and more art than any other figure. And no controversy has ever been fiercer than the one about his life and its significance.

Nicky Gumbel: An alpha male

But one certainty can be affirmed. The belief system is still a potent force, and could even be extending its influence through a strange event on 20 January, 1994.

On that day, at a concrete church next to Toronto airport, 80% of the congregation suddenly fell to the floor, apparently singing in tongues.

It became known as The Toronto Blessing and provided the kick-start for the Alpha organisation, led by Nicky Gumbel, a minister at Holy Trinity Brompton in London.

In 1992, it ran five courses in Britain, essentially aimed at agnostics. By the end of 1999, there were 14,200 courses around the world, attended by one and a half million people.

Enough to suggest that Santa Claus may have to come up with something better than a flying sleigh and the chimney trick to oust the Christ that christened Christmas.