I absolutely love Christmas. Seriously I do. I even love the tacky, overpriced, commercialised bits of it that people tell me I'm supposed to hate. It's the potential for generosity in it all that I love. Why? I'll give you an example. I pushed the boat out a bit last Christmas and gave my mother a mobile phone. Her face was a treat - so excited! I phoned up on Boxing Day to find out how she was getting on.

There was no reply at all from the mobile phone, so I resorted to the land line. My father picked up the phone, and I asked how she was managing with the charging, and the texting, and the directory, and the messages, and the entering of the phone numbers, and the voicemail, and the .

I could tell from my father's silence that it wasn't going as smoothly as I'd hoped. "Well," he said. "It's a bit of a struggle to understand."

I was slightly frustrated, because I'd spent a long time going through it. "Pass the phone over to her," I said. "I'll give her some more instructions."

I could hear him hesitating.

"It's OK," I said. "Just give her the message."

He went away and came back a moment later. He said: "Well, she says that in all honesty she doesn't want better instructions or more messages. If she's going to understand the wretched thing, what she really needs is her son to visit in person."

That is why Jesus came to earth. If we are going to understand how to live and how to be at one with God, God could have sent better instructions and more messages for a million years. But it wouldn't have achieved what was needed. So the Son visited in person. A human amongst humans. God amongst those who desperately need God. Jesus.

It's an extraordinary thought! God looked at his own earth, ruined by wrongdoing and failure, and lamented, 'What can be done?' But from the depths of time eternal Jesus Christ (or as the Bible refers to him, the Son of God) has always known what has to be done. So he slips on a pair of Levi jeans, he reaches for a Marks & Spencer sweater, he slaps on some aftershave (or whatever the equivalent was 2,000 years ago). And he says, 'OK, I'll go!'

And there he is. Walking along the high street. Among us.

All that tackiness? All that commercialism? I know it's not ideal. It's over-the-top.

But if what Christians believe is true - that Jesus Christ was God on earth - then it is so phenomenal that only an over-the-top response seems good enough.

Peter Graystone is co-ordinator of the Christian Enquiry Agency