For me it was when I was six years old and was taken to see him in his Grotto. My Mum siad I could go in on my own as I was growing up. he lifted me up and sat on his lap which had a big long lump in it. After we'd spoken for a while he told me that he had to go and 'feed his deer'. Imagine how I must've felt, how excited I would be to actually be able to see them all, especially Rudolph who was my favourite reindeer! So I waited outside the Grotto enterance and followed him unseen. My heart broke when I followed him to the gentlemens' toilet (rest room in american english) and saw what he did there, it certainly had nothing to do with feeding the reindeer who I never saw! In tears I ran and found my Mum who'd been shopping elsewhere in the big department store, and told her what I saw. She became very angry and took me to see the store manager, who asked me to tell my story. I don't know what happened after that but when Mum took me shopping there the next week there was a different Father Christmas, he seemed shorter than the other one, and my Mum held on to my hand really tightly and wouldn't let me go into the Grotto again.
It was only as I grew up that I realised what had happened, and to this day I can never see a live Father Christmas without repressing a shudder.