The story of Santa Claus brings festive magic on Christmas morning to kids all over the world.
Many parents dread the day their children ask them tricky questions about the big man in red.
But with friends gossiping in the playground and the internet providing an easy way to search for info, it's almost inevitable children are going to try and find out "the truth" for themselves.
We chatted to heads of parenting groups and our HuffPost UK Parents Facebook audience to find out when you should have "the chat", what you should say and how to deal with tricky questions.
"Opinions vary on the best time to break the news about the big fella in the red suit," explained Justine Roberts, Mumsnet's CEO.
"Some parents like to keep the magic going for as long as possible; some believe firmly that telling untruths to children is never OK, and a few are firm believers in Santa themselves.
"That said, most find that their children are pretty clued up well before secondary school - which is probably for the best, unless the child concerned is immune to teasing."
Anne-Marie O'Leary, Netmums' editor in chief said this is a hotly-debated topic on forums each year.
She agreed there is no "right" time to do the big reveal, adding: "Only parents can judge when they think their child is ready".
She said: "By 'ready', I mean not just to handle the news themselves, but also mature enough not to share it with younger siblings or friends who still believe."
We asked the HuffPost UK Parents audience on Facebook for their opinions on the hotly debated topic, and many agreed that when you choose to tell your child very much depends on their own personality and circumstances.
But something else interesting came out of the discussion: some parents never actually tell their children Santa isn't real.
"I've never told my kids - my eldest is 12 and he found out through friends at the age of 10," said mum Claire.
"My eldest daughter is nearly 10 and she's on the fence whether to believe or not. I let them believe as long as possible.
"I always say if you don't believe you don't receive. I'm a big kid at Christmas - I tell the older kids that I believe and get upset when they say Santa is not real."
Mum-of-one Helen said she hasn't told her son either and is happy for him to pretend he still believes or just find out for himself.
"He still believes but his friends say it's their parents. I left it at that," she wrote. "Even if he doesn't believe I'm glad he pretends he does."
"I'm 22 and my parents still haven't told me. And I don't plan on having this chat with my children either," added Rebekah.
Siobhan Freegard, founder of parenting video site Channel Mum is a firm believer children should be led to believe for as long as possible.
How can you do this? Respond to their tricky questions with clever answers.
"When your child asks you 'Is Santa real?', I'd ask two questions: 'Why do you ask that?' and 'Well what do you think?'. Then you can judge the next step based on their response," advises Freeguard.
"If they seem to be on the fence, don't lie outright but deflect their questions by saying 'anyway lets carry that chat on later, now we need to...'
"Or 'well whatever you think, we should still write a letter telling him what you want, don't you think?'. Then you can move gently from believing to not believing over time."
She added: "Some parents tell their children early as they worry they'll be teased in the playground for believing, but in my experience, kids are generally very forgiving and accepting of who believes and who doesn't."
O'Leary shared Netmums guidance on how to answer other tricky questions. For example:
How do you know which one is the real Santa when you see lots of Santas in shopping malls and in shops?
"Santa is just too busy in November and December so he sends out a team of helpers that you might spot. Sometimes it's the real Santa, sometimes it's a Santa's helper but it's very difficult to tell."
How does he get down the chimney? What if I don't have a chimney?
"Don't worry if you don't have a chimney or even if you don't fancy him coming into your room. Santa will always find a way to deliver the presents. He uses magic to get in and leave them for you."
How can he get around the world in just one night?
"This is the big question. You can find a site called Track Santa. We think they explain perfectly how he gets around the world in just one night and they also track him via satellite on Christmas Eve. So you can see where he is and how close he is to getting to your house."
At some point, you might be faced with a situation where you just can't deflect the truth. So then what?
Mum Wendy Harris told HuffPost UK Parents: "I told my son at the age of eight Santa had to have money sent to him to help make the toys because he can't always make everything.
"Now he's nearly 13 and he gradually began to understand what goes on, because of how we told him - he now knows we buy them and not Santa."
Another mum, Karis Flower, said she waited for her daughter to tell her that she was ready to know the truth. She said: "My oldest daughter begged me earlier this year to tell her the truth as to whether he is real or not.
"She is six and seemed able to take it and was fine. Wait for them to give you the evidence and ask you outright."
Many parents referenced a popular letter that has done the rounds online which helps parents tell their children.
The letter derived from a mum in America's response to her daughter asking her, which was then posted on Pinterest.
It begins: "Thank you for your letter. You asked a very good question: "Are you Santa?"
"I know you've wanted the answer to this question for a while, and I've had to give it careful thought to know just what to say.
"The answer is no. I am not Santa. There is no one Santa. I am the person who fills your stockings with presents, though. I also choose and wrap the presents under the tree, the same way my mum did for me, and the same way her mum did for her."
Read the full letter template here.
At the end of the day, the majority of parents believe keeping the magic of Christmas alive is the most important. So what if they're 26 and you still pretend Santa is real?
Freegard added: "However you choose to tell your child, remember the magic of those special memories of Santa continues long after that moment of truth - and even now on Christmas Eve I sometimes think I can hear sleighbells in the distance."