The image is from a stained glass window in St Magnus Cathedral, Kirkwall.
The life of St Magnus (d.1117) is well documented as he was the joint earl of Orkney, murdered by his cousin and commemorated by his nephew, who had the cathedral in Kirkwall built in his memory. His remains, and those of his nephew, are buried in the pillars of the cathedral. He is commemorated at Banniskirk by Watten, Shebster and Spittal. The ‘hospital of St Magnus’ is mentioned in a royal charter in 1476. Banniskirk may be a corruption of his name. His fair was formerly held at Watten-Wester in Caithness around the time of his feast on 16th April, known in the Middle Ages as Magnusmas. There is also a link with Dunbeath as records show that there had been plans to create a trading burgh at Inver called Magnusburgh. There are no other known dedications to Magnus in Scotland. There are a few in England, the main one being at Southwark Bridge, London. He is also remembered in Roskilde, Denmark.