[Bazf]

A shortened version about old St Nick.
English Father Christmas became part of the greater European Santa Claus in the 1950's. But until then he was quite a different character. His origins were steeped in the Viking lore, brought by these people when they conquered Britain in the 8th - 9th centuries. Although the Celtic Christians were brought in line with Roman practice from a decree at the Synod of Whitby in the 7th century, Christianity was still somewhat isolated from mainstream Europe. Many of the images in the Saxon churches were Byzantine in style not Roman. Even after the Norman invasion in 1066, when the Normans effectively wiped out all the early imagery and replaced it with Roman style, still oaths were commonly sworn "By God and by Odin". Things changed only slowly.
The Saxons welcomed King Frost, or Father Time, or King Winter. He would be represented by someone, given a fine hat or crown to wear and brought to their firesides.
In England in the Middle Ages, a parish would hire an actor, or often a cleric from another parish, to dress in disguise, and visit homes to see how people were doing. Maybe someones children were sickly because they had no food, or a widow was not managing now her husband had died - He would report back to the Parish priest, who would keep an eye on the situation.
Father Christmas was banned by the Puritans under Cromwell in the mid-17th century. He went 'underground' along with Minced Pies, Christmas games and the like.
In the 18th century, he began to appear in the Christmas plays of itinerant players. In the middle of the play, he would appear, heavily disguised, shouting his challenge, "In comes I, Old Father Christmas. Be I welcome or be I not - I hope that old Christmas will never be forgot!"
By the 20th century, he was a common figure in most Department Stores the length and breadth of the British Isles. He was often austere looking still, and he would ask children questions about their prayers, their reading, writing and arithmetic. If they had been naughty, he would tell them they must improve or he would not visit them at Christmas. But most people over the age of 50 will still refer to him as 'Father Christmas'.
After WWII, there was a great deal of American influence, and that, together with increasing advertisements by the Coca-Cola Company in the British press, changed the image of Father Christmas permanently. Now, he is always fat, always jolly, never admonishes children about whether they are good to their parents, or questions them on their catechisms and schoolwork. He is just a 'Jolly Elf', who goes by the name of Santa Claus, which as everybody knows, is the popular nickname of Saint Nicholas - Santa - Saint; Claus - diminutive for Nicholas.