The Reverend John Walker paid for the east window of Holy Trinity church in 1470. As was customary during the Middle Ages, Walker's own image was included in the window for which he had paid. This image would normally be associated with an inscription appealing for those in the church to pray for the donor's soul - of benefit to the donor on their journey through Purgatory, the afterlife.
John Walker appears in the window wearing a red ecclesiastical gown, a very expensive colour for the day. Images of the donor were often about displaying their wealth and influence as much as a show of piety.
There are many images of stained glass window donors in churches in the city of York, where medieval stained glass in particular survives in abundance. Many of the stained glass panels painted in York were imported from the Continent owing to superior manufacturing processes.