It was written as a very slow march with the Latin name of Adeste Fideles in the 1740s by John Francis Wade.
It was 10 years later that a musical colleague persuaded Wade to revise it into its better known, more rousing version.
Now people in Lancashire will have the chance to hear the original - sung from the oldest known copy of the original manuscript.
That copy is in the archives of Stonyhurst College, and this year, for the first time in living memory, the carol will be sung at the college in the manner in which the composer first intended.
The mixed choir of Stonyhurst College and St Mary's Hall will sing the carol at their public carol service, which is being held in St Peter's Church on December 5th at 7-30 p.m. The congregation will be given a copy of the manuscript printed inside the order of service, which they can take away afterwards.
There are only five known copies of the original manuscript of the carol, which was written by Wade when he was choirmaster at Douai College in France.
The Stonyhurst manuscript is thought to be the oldest signed and dated in existence.
"There was an earlier copy," said Jan Graffius, the college's curator, "but it was lost during the Second World War.
"Our copy is in our archive, but how it came to be there I haven't the slightest idea. Perhaps it came here because Douai is a Catholic college and so are we. It is a very pretty publication with the staves in red ink and the notes in black."
Robin Highcock, director of music at the college, said: "Stonyhurst College has always sung Adeste Fideles in Latin, and once more this year we will be singing Wade's wonderful words and melody. The carol, which concludes the service, will be sung with the true Stonyhurst spirit."
As the popularity of this tune spread, "apprentice boys whistled it in every street: it was even said that the blackbirds in the square joined in the chorus".
The carol service will be candlelit and all will be welcome at St Peter's Church.