Your debit / credit card is just a bit of plastic, isn't it? Approximately 85mm x 55mm of plastic, actually (I just measured it). And yet, when you think about it, it's a whole lot more than that.

I've just been upgraded - whoopeeewoo - from a "normal" Barclaycard to a "gold" card. Heaven knows why, or what this means, but anyway. However, I've had my old Barclaycard since Oxford days. With that card I will have purchased my finalists champagne, my graduation gown, the furniture for my flat, my first suit for work, endless meals and bottomless tanks of petrol. It's been with me to New York, to Hong Kong, and now I'm just cutting it up with a pair of scissors and replacing it for a younger, brighter model.

Now, before you think I've totally lost the plot (or, indeed, turned into Ollie as I'm sure this is the sort of observation he'd make) it just came to me how much we rely on one moderately small piece of plastic. We may just take it in and out of our wallet mindlessly, but it's always there. It's at Tesco week-in week-out and then accompanies to some fancy restaurant when you're feeling flush. And of course it's 16 digit number is the crux of online shopping and gambling (- a new one on me but Ollie persuaded me to purchase a Euromillions lottery ticket the other night, so I did - watch out for his scam though, he's charging a 5% finder's fee if I win). You can even withdraw cash with it. So, there we are. We may take it for granted but really it is the key to much. Almost everything, in fact. And all in a bit of plastic.