It was written as a political song about death. But Cliff Richard's Mistletoe and Wine, which turns 25 this month, turned into something very different.
The song emerged in HTV's screen adaptation of the Hans Christian Anderson story The Little Match Girl, itself adapted from the 1976 stage musical Scraps, by Keith Strachan, and screenwriters Jeremy Paul (who died in 2011) and Leslie Stewart.
"The story is about a kid who freezes over the Christmas period who imagines herself in a better world," explains Strachan.
"The sentiment of the song was meant to be that people didn't care about the poor - it's a socialist Christmas song. It was a song about the middle classes' lack of concern."
Despite the strong source material, lyric writer Leslie Stewart nearly didn't complete it.
"I told them 'why don't you find a Christmas carol?' and someone said 'Yeah, we can do that but why don't you write your own song?'" he recalls.
"I was walking along the river in Ware taking my dog for a walk and 'A time for giving, a time for getting, a time for forgiving, and for forgetting' popped into my head. That was it! That's the song.
"Keith and I used to write on answer phones. I would ring him and say 'don't answer your phone' and leave a message on the answer phone. Keith rang me two days later and said 'listen to this.'"
Performed by carol singers on stage in 1976, the song became "a music hall pub version" for the TV show, sung by a good-time-girl character played by Twiggy.
"It was a lively show to work on, and I have very happy memories," the model recalls of the programme, which also starred The Who's Roger Daltrey.
Strachan, who wrote the song "on a piano in half an hour" sent "a more poppy demo" by Jeremy Paul's 12 year-old daughter to Cliff Richard's then-manager Peter Gormley.
"It was a pub song," recalls Sir Cliff. "The lyrics were all about a drink and a smoke and a laugh and a joke, and I asked my manager 'do you think they'd mind if I change the lyrics?'"
After Sir Cliff, who refused any writing credit, added some religious references, he "hung a bit of tinsel" in a Wimbledon recording studio in July 1988 to record his own version.
"As soon as I added those lyrics," he says, "that made it a Christmas song".
Leslie Stewart, to put it politely, was not a fan.
"I hated it," he says. "I found the lyrics offensive. I'm not a practising Christian.
"I didn't really know about it until I heard the demo, and then I heard about the verse he wanted to do. But to be fair, he made it his song."
Asked today if he faced any complaints from the writers, Sir Cliff says: "None, whatsover".
"I just felt that I wanted to bring back the spiritual aspect of Christmas. Slade did some fabulously festive hits but they weren't actually about Christmas.
"People won't become Christians because you sing about your faith - they either like the song or they don't."
Twiggy says she "wasn't surprised when Cliff recorded it as a single and it became a big hit."
Sir Cliff had similar instincts: "I thought it might be a big hit. For me a big hit is to be in the top five.
"I don't subscribe to the view that if you're not number one, it's a failure. Maybe that's why people disappear so quickly these days, because they have that attitude."
For his part, Strachan had always been convinced he had a hit on his hands - he just "couldn't persuade people to do it".
"I asked Dennis Waterman if he fancied doing it. Val Doonican sent me a very nice letter saying 'thanks but no thanks', and I thought 'maybe this is not as good as I thought it was'.
"But I turned out to be right."
The song sold more than 750,000 copies, becoming Sir Cliff's first number one of the decade, and the country's biggest selling song of 1988. It would spend four weeks at number one over Christmas.
"That's the hardest time to have a number one," argues the singer. "Everybody and their wife recorded a Christmas song. You know that you are going to have to do well against some excellent artists.
"People associate me with that time of year, but I have only had two Christmas number ones in 55 years!" (Saviour's Day is the other).
Sir Cliff, who has just released his 100th album, says he would no longer compete in the Christmas marketplace if he discovered a song like Mistletoe And Wine.
"I'd be tempted to do something again but it would almost be more fair to the writer to record it with a new band," he explains.
"Airplay is vital for single hits. The only way I can have a fair competition is if your records are on the radio - gone are the days where the likes of myself, Elton John, Tina Turner, Phil Collins have our records played.
"There is an ageism in the radio industry. If you ask me to record a new song, I'm not sure it would get the support it needs."
Not everyone is a fan of the song - coffee chain Costa recently pulled the stunt of banning it from its stores after customers voted on the "least popular Christmas Song" - as Sir Cliff understands.
"I often wondered if it made me have such a trying time with Millennium Prayer," he says, of his number one from December 1999.
"That was one of the hardest number ones I have had. I was confused by all the negative reaction and Mistletoe and Wine may have kicked that off.
"I had found myself in the charts way past my [supposed] sell-by date and maybe that annoyed people."
Composers Stewart and Strachan have learned to embraced Sir Cliff's version. "I resisted it for a long time but once I heard it on a car radio a few years later, I thought, 'this is OK'," says Stewart.
"It's not a happy Christmas song, it's about a girl dying and so it's a new song to me - the one I co-wrote and the one I hear every Christmas. Really it's Mistletoe and Wine 2.0 and I can't tell you which I prefer.
"It's a song I wrote but not the song I imagined - but it's part of the English Christmas."
The royalties, from which Sir Cliff did not benefit, may have helped change their minds.
Both writers decline to divulge figures, but Stewart calls them "a welcome trickle" and Strachan says that they paid for "a holiday, but not a house."
For Strachan, Mistletoe and Wine wasn't even his most lucrative piece of music.
Ten years after Sir Cliff's song became the biggest selling hit of 1988, he was asked to write the theme tune for a new TV show.
The name of the programme? Who Wants to be a Millionaire?