Trial by Seven of Duncan the Tall

The trial by seven of Duncan the Tall was a major event in the life of Ser Duncan the Tall, which had unexpected repercussions across the realm.

Background
While attending a tournament at Ashford in the Reach, Ser Duncan the Tall, a poor hedge-knight, became smitten with a beautiful Dornish woman. However, the arrogant Prince Aerion "Brightflame" Targaryen accosted the young woman, at which Ser Duncan sprang to her defense - as any true night should - and struck Prince Aerion. To strike a member of the royal blood was treason, but through a series of events Ser Duncan demanded not only a trial by combat, but a rare "trial of seven", involving two teams of seven men each.

Ser Duncan's side was victorious, but during the combat Aerion's uncle Crown Prince Baelor "Breakspear" Targaryen accidentally took a severe head injury, and the resulting concussion killed him. As a result Baelor's younger brother Prince Maekar became the new heir to the throne, Aerion's own father.

In the books
The trial by seven of Duncan the Tall is the central event of the first installment in the Tales of Dunk and Egg prequel novellas set 90 years before the events of the main A Song of Ice and Fire series.