Every Easter in Jerusalem, there is a ceremony at the church of the Holy Sepulchre.

Wikipedia is a fairly superficial source, but it serves here to give the basics.

“Orthodox tradition holds that the Holy Fire happens annually on the day preceding Orthodox Pascha (Orthodox Easter) in which a blue light emanates within Jesus Christ’s tomb (usually rising from the marble slab covering the stone bed believed to be that upon which Jesus’ body was placed for burial) now in the Holy Sepulchre, which eventually forms a column containing a form of fire, from which candles are lit, which are then used to light the candles of the clergy and pilgrims in attendance. The fire is also said to spontaneously light other lamps and candles around the church. Pilgrims and clergy claim that the Holy Fire does not burn them.

While the Patriarch is inside the chapel kneeling in front of the stone, there is darkness but far from silence outside. One hears a rather loud mumbling, and the atmosphere is very tense. When the Patriarch comes out with the two candles lit and shining brightly in the darkness, a roar of jubilation resounds in the Church.

Thousands of pilgrims as well as local Christians of all denominations gather in Jerusalem to partake and witness this annual event. The Holy Fire is taken to certain Orthodox countries, such as Greece by special flights, being received by church and state leaders.”

The ceremony in essence has not changed in long over a thousand years and it is almost certain that William Marshal and his men would have witnessed and been a part of this service twice before they returned home from Jerusalem.

Here is the first time from TEMPLAR SILKS

The church of the Sepulchre waited in darkness.  William could hear people breathing and shuffling around him.  The murmur of prayers, the intense moment of waiting for the breath of God to kindle the lamp in the tomb of Christ and restore light to the world.  Like everyone gathered in the Round outside the Edicule, he clutched a candle, ready for the moment, filled with belief, but at the same time, deep under the surface, assailed by a treacherous darkness of doubt.  What if the flame did not kindle?  What if the weight of their sins was too great and God chose to show his displeasure by denying the light?

Another part of him wondered about the lies men told to comfort themselves, and a cynical part of him wondered just what the Patriarch was doing alone within the Edicule without witnesses.  What conferred on him, a worldly prelate who dressed in jewelled silks and kept a lovely young mistress, the privilege of receiving the Holy Flame, symbol of Christ’s resurrection?  He strove to quash that thought and murmured his prayers like everyone else.  Even if the fire was caused by human intervention, it did not negate the miracle of Christ’s death and resurrection.

Baldwin’s litter had been borne as close to the Edicule as possible, and since his leprous fingers were unable to grasp the candle, his little nephew, heir to the throne, held it instead in his small, perfect grasp, his gaze clear and steady and his infant features petal-smooth.  His mother stood at his side; she had come to Jerusalem for Easter under safe conduct to make peace with the king, but would soon to return to Ascalon and her husband. It was tacitly understood that Guy would keep his distance and only Sybilla would visit the court as necessary.

The waiting time lengthened and the prayers developed an edge as tension escalated in the packed rotunda. Somewhere a child wailed and was shushed by its parent.

Suddenly, a sound like rushing wings came from within the Edicule, then a soft cry of triumphant elation and Heraclius emerged, ducking under the arch and then standing straight in his glittering patriarchal robes, light shining around him.  He held a burning candle in each hand and the flames shone a strange, ethereal blue that sent a gasp around the rotunda.  Priests hastened to light bundles of tapers from the Patriarch’s candles while Heraclius himself stepped forward to kindle young Baldwin’s taper.

In widening circles the rotunda filled with a blaze of heat and light as the fire was sent from person to person, no longer ethereal blue, but customary gold, and wisping with smoke that filled the rotunda with the smell of burning wax.  William took the flame from Onri and passed it on to Eustace and Ancel, who in turn passed theirs to the rest of the men and as the wicks flared, the cry went up that Christ was risen and mankind saved.  Amid chanting, praise and joy, the light was borne in procession out into the streets of Jerusalem and shared among its relieved and joyful citizens.  William’s heart brimmed with bliss and humility and a tender, almost painful feeling that he was unworthy and should strive to be a better man. All at once his cheeks were wet as a sob shuddered through him.

Ancel touched his shoulder in concern. ‘Gwim?’

He shook his head. ‘I was thinking of Harry and how we are witnesses for him.  He should have been here to see this and kindle his own flame, but we are here in his stead. This light is for all of us, but it is for him especially.’