Years ago, when I had to sell the idea of shopping online to my parents on a lazy Sunday afternoon, all they said was it would never take off. My stock response was "course it will - its all about convenience and speed".

But what does that mean? - is that really all that shopping online has to offer?

It means different things to different people - to me it means that driving to buy a new high chair this weekend, an 80 mile round trip, would cost more in petrol than the postage John Lewis would charge me.

I don't know what the tipping point is, but for me it is here - shop online - it is cheaper than driving, it is greener and far more convenient.

So at least now I have a new answer.

Next time my parents ask me i'll say "it is cheaper than driving".