The traditional Yule log is a survivor of Pagan celebrations to mark the Winter Solstice, the time when the sun appears to stand still in the sky, before the days begin to grow gradually longer on the approach to spring.
It was extremely bad luck to buy a Yule log. It must either be gathered from the householder's own land, or be received as a gift. The most commonly used wood was ash, and the log must be big enough to burn for twelve days.
Once it was dragged into the house it was decorated with greenery and doused in ale or cider before it was set alight using a sliver from last year's log. Each day a little more of the log would be pushed into the hearth as it gradually burned away and, at the end of twelve days, it was put out with water.
These days, when very few people own their own woodland, and most of us have hearths that are far too small to hold a log that's long enough to burn for twelve days, we are more likely to represent a Yule log in chocolate!