st. andrew was supposedly crucified in this position (x as opposed to +) and he's the patron saint of scotland.
or:
"One legend, (very much a story but of interest nonetheless), concerns the fact that it is believed by generations of Scotsmen that our national flag, the white saltire on a blue ground, the oldest flag in the British Commonwealth, originated in a battle fought, a little more than a mile from present day Markle, in the Parish of Prestonkirk in East Lothian, in the Dark Ages between the Picts and Scots on one side and the Angles of Northumbria on the other. There are various versions of the tale but it is generally agreed around the time of the 8th century, an army of Picts and Scots under King Hungus found themselves surrounded by a force of Angles under their leader Athelstan. King Hungus prayed earnestly for deliverance to God and the saints and that night St Andrew appeared to the King and promised them victory. Next day, when battle was joined, the vision of the white saltire (the diagonal cross on which the Apostle had been martyred) was seen by all in the blue sky. This so encouraged the Picts and Scots and affrighted their adversaries that a victory was won. King Athelstan was slain at the crossing of the burn, still known to this day as Athelstaneford. The story continues that this all was seen as a 'Miracle' and may have been the origin of the name "Markle"! In the nearby East Lothian village of Athelstaneford, a flag heritage centre commemorates and discusses the development of the legendary white cross on the blue background."
from: http://www.celebrationofcelts.com/scotland.html copy
