. Easy. Later that year, one more episode was recorded and broadcast, commonly known as the Christmas episode. It contained no reference of any kind to Christmas. It was called the Christmas episode because it was first broadcast on December 24, which is not Christmas Day. After this, things began to get increasingly complicated. In the fall of 1979, the first Hitchhiker book was published in England, called The Hitchhiker's Guide to the Galaxy. It was a substantially expanded version of the first four episodes of the radio series, in which some of the characters behaved in entirely different ways and others behaved in exactly the same ways but for entirely different reasons, which amounts to the same thing but saves rewriting the dialogue. At roughly the same time a double record album was released, which was, by contrast, a slightly contracted version of the first four episodes of the radio series. These were not the recordings that were originally broadcast but wholly new recordings of substantially the same scripts. This was done because we had used music off gramophone records as incidental music for the series, which is fine on radio, but makes commercial release impossible. In January 1980, five new episodes of "The Hitchhiker's Guide to the Galaxy" were broadcast on BBC Radio, all in one week, bringing the total number to twelve episodes. In the fall of 1980, the second Hitchhiker book was published in England, around the same time that Harmony Books published the first book in the United States. It was a very substantially reworked, reedited and contracted version of episodes 7, 8, 9, 10, 11, 12, S and (in that order) of the radio series "The Hitchhiker's Guide to the Galaxy." In case that seemed too straightforward, the book was called The Restaurant at the End of the Universe, because it included the material from radio episodes of "The Hitchhiker's Guide to the Galaxy," which was set in a restaurant called Milliways, otherwise known as the Restaurant at the End of the Universe. At roughly the same time, a second record album was made featuring a heavily rewritten and expanded version of episodes 5 and of the radio series. This record album was also called The Restaurant at the End of the Universe. Meanwhile, a series of six television episodes of "The Hitchhiker's Guide to the Galaxy" was made by the BBC and broadcast in January 1981. This was based, more or less, on the first six episodes of the radio series. In other words, it incorporated most of the book The Hitchhiker's Guide to the Galaxy and the second half of the book The Restaurant at be End of the Universe. Therefore, though it followed the basic structure of the radio series, it incorporated revisions from the books, which didn't.