|In 54–59 AC
After King Jaehaerys I Targaryen wed his sister, Alysanne, Jaehaerys sent seven preachers to walk the realm and win the smallfolk over to the marriage, not with swords, but with words. Septon Alfyn was among these seven. They traveled the realm alone, walking from village to village, telling the smallfolk of Jaehaerys's wisdom and Alysanne's kindness. When challenged on the issue of incest, the seven would say the Valyrians mounted dragons and thus were not like other men, and as such, an exception had to be made.
When the High Septon died in 54 AC, the king and queen hoped to prevent the election of a High Septon that would denounce their marriage as incestuous and begin an uprising. Septon Mattheus of King's Landing was a likely candidate, and fiercely opposed to the Targaryen practice of incest. King Jaehaerys and Queen Alysanne flew to Oldtown, and according to Septon Barth's account there struck a deal with Lord Donnel Hightower to support Alfyn, a fierce champion of the Doctrine of Exceptionalism, as the new High Septon. King Jaehaerys promised Lord Donnel that, as Alfyn's old age would likely mean he would soon die, Alfyn's successor would be a Hightower on the condition that the Hightowers would support the king's doctrine.
At Ashford, Alfyn was astonished to learn he had been elected High Septon. It took him a fortnight to travel to Oldtown and take up the crystal crown. Alfyn and his successor, a brother of Lord Donnel Hightower, made the Doctrine of Exceptionalism an official tenet of the Faith of the Seven.