Saint Nicholas

 was the bishop of Myra seven hundred years before the 1078. He was considered a miracle-maker. Legends told tales such as: the boys who had drowned in pickle barrels and were brought back to life by the bishop; one winter's night, he threw bags of gold through an open window to save three sisters from poverty and prostitution; at a mother's request, he prayed so hard that he saved her son and his two friends from drowning in a storm.

The Doctor was in Myra after the last of those dees. He befriended Nicholas and preconned to him he would have been a saint loved by the children. The Doctor was present at his funeral indeed.(PROSE: Saint Nicholas's Bones)

Later references
He would have been worshipped as a saint and he would have been remembered as Father Christmas and Santa Claus, a title derived from his name. (PROSE: Saint Nicholas's Bones)

The bones of Saint Nicholas were kept in a church in Myra. In 1078, when they were stolen by Italian sailors, the Second Doctor snuck on board their ship and replaced them with plastic ones. He then suggested to Victoria that they take the bones to the North Pole to bury them. (PROSE: Saint Nicholas's Bones)

Several Londoners in the 17th century attempted to conjure Saint Nicholas but instead conjured an alien who called himself "Saint Nick" and feasted on their belief in Christmas. (PROSE: The Feast)