With Easter just three weeks away, many have begun focusing on the final days of Jesus Christ, his crucifixion and his resurrection.

Central to those events was the cross upon which he was nailed.

The cross is one of the universally recognised symbols of Christianity, representing Christ, his Passion and his Church. It is made by two straight lines intersecting at right angles.

But in the first three centuries after Christ's death, the cross was not openly used as a Christian symbol.

According to the book Christian Symbols, Ancient and Modern, early believers looked beyond the Crucifixion to the Resurrection and placed emphasis on the promise of life with Christ on earth and beyond the grave, not on the cross of suffering and humiliation.

The book claimed that one of the earliest representations of the crucifixion was a derisory graffito found in Rome.

Another was a tiny third-century representation from Constanza -- now on display in the British Museum -- which shows Christ standing symbolically with his arms outstretched against the cross.

According to legend, it was not until the reign of Emperor Constantine that the cross was publicly displayed and accepted as a symbol of the Christian faith.

The "Father of Church History'', Eusebius, Bishop of Caesarea claimed that Emperor Constantine was asleep, on the eve of a battle, and saw in a dream a luminous cross in the heavens bearing the words "In hoc signo vinces'' -- "In this sign conquer''.

The Emperor ordered that the words and cross be placed on the imperial standard and under this banner the Emperor won a victory over his rival.

According to the Bishop, from that triumph the monogram became a sign of victory and was widely recognised as meaning salvation in the name of Christ.

Legend also has it that Emperor Constantine's mother, St. Helena, discovered the Cross used to crucify Christ, known as the invention of the Cross.

Reportedly, St. Helena frightened Jews into revealing the site of the three crosses which were buried deep in a pit.

The True cross was allegedly identified by a miracle of healing and afterwards a martyrium was built on the site.

The book Christian Symbols, Ancient and Modern added: "Whether this attractive legend has a foundation of truth or not, it is a fact that the belief in the finding of the True Cross increased the devotion of the faithful and dramatically stimulated the use of the cross as a symbol in art.''