Is 'The holly and the ivy' a Christian hymn or a pagan fertility song? Are Christmas carols necessarily religious at all? Sir Geraint looks back to medieval times and beyond. The carols sung are: 'The holly and the ivy', 'Deck the halls', 'The boar's head carol', 'The old grey goose'.

How did carols come to tell of Christ? In today's programme Sir Geraint shows how the church in the Middle Ages began to sell the Christmas story to the people at large, by taking over popular forms of entertainment that already existed. The result was that from Medieval mystery plays to modern nativity plays, drama, dance and carols came together to express the joy of Christmas. Today's carols: 'Ding dong! Merrily on high', 'The Coventry carol', 'The cherry tree carol', 'Shepherds have left their sheep', 'Personent hodie'.

What was St Francis's role in the history of Christmas? And what do the three ships in the carol of the same name have to do with the story of Christ? In today's programme Sir Geraint looks across the Channel to see how carols that started as 'Noels' in Europe turn out to be among the most popular sung in Britain today. Today's carols: '0 come, 0 come, Emmanuel' 'In dulci jubilo' 'I saw three ships' 'II est n6 Ie divin enfant' 'Orientis partibus'

Why was Christmas banned by law? The founder of Protestantism, Martin Luther , wrote carols, but the Puritans denounced them as pagan or popish or both. But when the monarchy was restored to England, so was Christmas and Carol writing began again. Today's carols: 'Away in a manger', 'While shepherds watched', 'We three kings', 'The waits carol' ('Greensleeves'), "The three kings'.

Why does the Grey Mary return each year? And who really went a-wassailing? In the fifth of seven daily programmes Sir Geraint looks at the local carol customs which survived down the centuries. In Cornwall the male voice choirs of the mining regions sing their own Christmas hymns; Wales has both old winter festivities and a unique kind of carol; Somerset and Yorkshire are among the areas where the wassail bowl was filled. Today's carols: 'Now the holly bears a berry', 'Here we come a-wassailing', 'Lo, he comes an infant stranger', 'The Mari Lwyd ceremony song', 'The Drayton wassail'.

Sir Geraint looks at the way carols were rediscovered in the 19th century, from the clerics who chanced upon a Latin text containing many now-famous carols, to folk song collectors Cecil Sharp and Ralph Vaughan Williams. Today's carols: 'Good King Wenceslas', 'Unto us is born a Son', '0 little town of Bethlehem', 'It came upon the midnight clear', 'The voice of God is heard above', 'Morning star O cheering sight'.

Why is 'White Christmas' as much a carol as 'In the bleak mid-winter'? The last of seven programmes looks at the modern Christmas, from Charles Dickens and Prince Albert to Johnny Mathis and John Lennon. Sir Geraint discovers that the modem celebration has changed little from Victorian times, and that a number of Christmas pop songs are modem carols.