Yesterday was the 1,700th anniversary of the proclamation of Constantine as Emperor of Rome, possibly at the location of the Roman fort where the Minster now stands.
Constantine is credited with a period of religious
tolerance which allowed Christianity to develop from an underground cult to a mainstream religion that went on to spread across the globe.
The Dean and Chapter of York hosted yesterday's service to give thanks for Constantine the Great and pray for the unity of the Church.
Guests included the Archbishop of York, John
Sentamu, the Orthodox Archbishop of Thyateira and Great Britain and the Episcopal Vicar of the Roman Catholic Diocese of Middlesborough,
Dean of York Keith Jones said the service under the central tower of York Minster celebrated an event of "momentous importance".
"When the troops proclaimed Constantine as their Augustus, possibly at this very place, they cannot have known that this young leader would within a few years have made Christianity the religion of the Roman Empire," he said.
"Still less can they have suspected how, from this date, the Christian faith would leave its mark on the institutions, monuments, and lifestyle of the world."
At the end of the public service Dr Sentamu waved off a colourful and noisy procession from the steps of the Minster, heralded by a fanfare of horns.
Led by Roman soldiers, more than 100 students and schoolchildren made their way to nearby Museum
Gardens with street performers and puppeteers, before the grand finale in the
gardens – a flight by a golden eagle.