This is the Danish flag, Dannebrog or “Danish cloth”. I found it draped over the pews while I was taking pictures inside the church up the road.
According to the Guinness Book of World Records it is the oldest continuously used national flag in the world. The current design of a white Scandinavian cross on a red back ground was adopted in 1625.
According to legend, Dannebrog originally fell from the sky on June 15, 1219 during the Battle of Lyndanisse near Tallinn in Estonia. This so inspired the Danes that they went on to defeat the enemy.