If you are a child who believes that Santa and his merry elves in the North Pole are responsible for your Christmas gifts, not your exhausted parents sweating at the sight of their credit card bills, then stop reading now. Grinches, non-believers and those who enjoy schadenfreude can step this way.
Journalist Sarah McCammon's six-year-old daughter sparked some smiles among Twitter users after her mother shared a strongly-worded letter she had written to Father Christmas, telling him he has an "emty" life. It seemed that she was on the edge of realising that Santa was a lie, suggested McCammon.
In that spirit, we asked people to share the moment they or a loved one realised that Santa was not real.
THE SANTA ILLUSION
"I was on the bus with mum and my younger brother when I realised that Santa wasn't real. But I was aware enough not to keep asking questions so that my brother didn't find out. So I just sat looking out of the window thinking, reassessing my life. It was raining. I remember it like it was yesterday." Sasha Hopkins, 26, Brighton.
"My parents tried extra hard to be convincing because I had younger siblings. But one year I realised that Santa suddenly had the same handwriting as my mum. I went up to her like 'Erm... mum? Is this your handwriting?' and she was, replied: 'I don't know what you're talking about'." Toby, 26, London.
"I knew that my parents hid presents in the wardrobe but I thought they must send them to Father Christmas to deliver back to us. But I remember one year laying on my parents' bed and seeing a present wrapped in shiny paper glinting through a crack in the wardrobe. It dawned on me that the presents came from my parents." Michelle Jackson, 38, Bexley, Kent.
"One Christmas night I was at my aunt's and my family wasn't around to fill my stocking with sweets and toys. At first I thought Santa got confused by my change of address." Khaloo Vos Savant, 35, Mumbai.
"My family used to spend Christmas at my granny and grandad's in Derbyshire so all the presents had to travel up with us.
"My grandad said to my mum: 'Right let's get all these presents out the car'. Unbeknown to him my five-year-old brother was standing behind my mum. His face was one of total devastation." Francesca De Franco, 38, Surrey.
"I lived on a farm and my sister told me that Santa was too fat to fit down chimneys so he had to come in the front door. I was five and I refused to go to bed on Christmas Eve, scared stupid that this strange man would be wandering around the corridors. I insisted that he left my presents outside. This happened for the following two years until they had to tell me he wasn't real. To compensate, my parents told me we had fairies at the bottom of the garden." Louise Stewart-Muir, 50, London.
"I harboured suspicions about Santa ever since my father came home dressed as him to deliver a puppy when I was about three years old. I remember the confusion that settled on me: I had the feeling that Santa was someone I knew, but couldn't place my finger on who it was.
"Every time I stretched for the beard to get a peek at what was underneath, my father would slip out of reach. My parents still tell the story nearly every Christmas about how I ignored a puppy to satisfy my scepticism at the age of three." Vicente Camara, 25, London.
"I was in junior school when my best friend said to me one lunchtime, 'but you know Santa isn't real, right?'. I hadn't realised, but said yes. Really wanting to still believe, I tried not to give it much thought. Come Christmas Eve I struggled to get to sleep. I started to hear a few thumps and squeezed my eyes shut worrying that if I wasn't asleep, Santa wouldn't come. There was some creaking and then a loud bang right outside my door, promptly followed by an almighty expletive. I was sure Santa wouldn't swear at that volume and I was pretty sure he wasn't Scouse!" Laura, 27, Kent.
"Over the years I questioned my parents so many times but they went to great lengths to stop me doubting - even leaving letters from Santa when I had good grades. Then I confronted my sister who was 20 at that time, when I was 11.
"She said that Santa, like magic, is something personal and that even if he might not exist it was up to me to chose if I believed in the magic of Christmas or not. It made me feel like an idiot at first and just very lonely." Natasha, 27, London.