A Requiem Mass will be held for a priest who raised a blood-soaked handkerchief and guided the body of a dying teenager through army gunfire on Bloody Sunday.
Catholic retired Bishop of Derry Edward Daly, 82, has been lauded as a hero and fearless peace builder who walked with the people of his city in their darkest hours.
The cleric's use of the universal symbol for ceasefire during a massacre of innocent civil rights protesters by soldiers in January 1972 became an enduring image of the conflict. He died on Monday after a long illness.
His funeral today at St Eugene's Cathedral in Londonderry will attract a large crowd from across Ireland and beyond.
Dr Daly's sisters Marion and Anne, nieces and nephews will be among the chief mourners.
He will be buried in the cathedral grounds afterwards.
Many well-wishers and old friends have visited St Eugene's to see his body lying in repose.
In later life the retired bishop was reluctant to discuss the moment that arguably best symbolised his Christian ministry; in death it has largely defined him.
As a young priest he famously waved the bloodied rag as he led a brave group bearing fatally injured civil rights protester Jackie Duddy, 17, to safety in Londonderry in Northern Ireland on Bloody Sunday.
Paratroopers had opened fire and killed 13 people. Fourteen were injured and another was to die later.
Bloody Sunday has been described as one of the catalysts of IRA recruitment and the 30-year conflict which left more than 3,000 dead and many others injured.
Bishop Daly was a prominent witness at Lord Widgery's inquiry soon after the event, which exonerated troops from the Parachute Regiment, concluding that they had come under attack from gunmen and bombers.
The Bishop of Daly dedicated much of the rest of his life to clearing the names of all the victims.
He believed the violence of the Troubles was futile and morally unjustified and was an arch-critic of the IRA.
The head of the Catholic Church in Ireland Archbishop of Armagh Eamon Martin has lauded him as a fearless peace builder who took a personal interest in those who suffered miscarriages of justice.
His untiring advocacy for the Birmingham Six, the victims of Bloody Sunday and for the families of those murdered by paramilitaries earned him respect from some, suspicion from others.
Dr Daly was Bishop of Derry from 1974 until 1993, stepping aside after suffering a stroke. In recent years he had battled a long-term illness.