After Coel's death Constantius himself seized the royal crown and married Coel's daughter. Her name was Helen and her beauty was greater than that of any other young woman in the kingdom. For that matter, no more lovely girl could be discovered anywhere. Her father had no other child to inherit the throne, and he had therefore done all in his power to give Helen the kind of training which would enable her to rule the country more efficiently after his death. After her marriage with Constantius she had by him a son called Constantine.
- The History of the Kings of Britain, Geoffrey of Monmouth (translated by Lewis Thorpe)
Helena, the Mother of Constantine the Great, was held in high regard by Medieval men and women and she was recognised as an important saint. She was said to have embraced Christianity at an early stage and on a trip to Jerusalem it was claimed she had located the True Cross, an occasion celebrated in the liturgical year as the inventio crucis, the rediscovery of the Cross. Geoffrey of Monmouth, on behalf of the Britons, laid claim to Helena by pronouncing her British by birth and a royal princess by heritage, the daughter of King Coel of established legend. Not all chroniclers were equally blinded by enthusiasm, however. William of Malmesbury soberly followed the ecclesiastical tradition, leaning on Ambrose of Milan's statement that she was the daughter of a stable-boy. Matters of heritage aside she was revered and venerated throughout the Middle Ages and several churches were dedicated to her. One of these churches is St Helen's Church of York.
It is assumed that the veneration for Helena has long roots in the religious history of York, but the oldest sign of a church is the 12th-century font. The church itself has been rebuilt once in the 16th century and twice in the 19th century, but it is believed that the current design echoes that of the 14th and 15th-century architecture to a great extent, with the exception of the chancel built in 1857-58. Facing the church today is St Helen's Square, established in 1732 after the graveyard had been paved over and its bones removed to Davygate where gravestones still can be found.
Both the Anglican and Catholic branches of the modern church are today very aware that the historical Helena had no connection to neither York nor Britain. This is, however, of lesser importance, for in her posthumous life she had had an important place in lay religiosity of several parishes. This particular church, as stated, can only securely be dated to the 12th century, but there was in York also a second church dedicated to Helena, namely St Helen Aldwark which is no longer extant, but most likely of Anglo-Saxon origin. Whether her alleged connection to England, or for that matter York's historical connection to her son Constantine who was proclaimed Emperor by his troops at the Roman headquarter in the city, has in any way influenced her popularity can not be ascertained. She has nonetheless been embraced by York and a statue of her at the town hall.
The earliest reference to St Helen's Church in the sources dates from 1235, but not much of its 13th-century heritage survives today, the exception being a handful of spolia found throughout the church space. Masonry points to construction activity going back to the mid 12th century, and it is speculated that if there stood an Anglo-Saxon minster on this spot, its wooden structure may have been replaced by a stone church at about this time. The High Medieval architectural features are nonetheless scant, outweighed by the Late Medieval remnants such as parts of the stained glass. The 14th and 15th centuries saw the most significant part of the church's Medieval architectural emendations.
St Helen's Church did not have a large congregation and its priest had little in terms of income. Its Medieval parishioners were largely the glass-painters who lived and operated in Stonegate and several of the guild's members were interred in St Helen's throughout the 15th century. The glass-painters' motto was Da nobis tuam lucem Domine, give to us your light, Lord, and their work can be witnessed in the Medieval glasswork still extant in the church.